Hamburg, Germany (CNN) -- A group of jihadists from the German city of Hamburg is alleged to be at the heart of the recent al Qaeda plot to launch coordinated terrorist attacks against European cities, European intelligence officials said. 
 
 Western intelligence officials say they learned about the reported plot after Ahmed Sidiqi, a German citizen of Afghan descent, was arrested in Afghanistan in July and taken to the U.S. air base at Bagram for questioning. He has not been charged and intelligence sources in Germany say he is cooperating with the investigation. 
 
 In early 2009, Sidiqi and 10 others left Hamburg for the tribal areas of Pakistan -- where most joined a jihadist group fighting U.S. and coalition forces across the border in Afghanistan, according to German intelligence officials. 
 
 Sidiqi told American interrogators that at least one member of his travel group was to be a "foot soldier" in the plot, with other members of the group helping to plan the attacks, a European counterterrorism official told CNN. 
 
 Sidiqi divulges new, unverified information every day, the German intelligence sources said. 
 
 A German Foreign Ministry official told CNN Monday that German authorities have been given access to Sidiqi in Afghanistan. 
 
 The reported plan prompted the U.S. State Department to issue a Europe-wide security advisory for Americans traveling in Europe. 
 
 A homeland security official said Monday that a bulletin went out a day earlier to state and local law enforcement agencies advising them that the travel alert was issued based on intelligence they had already been made aware of. 
 
 The four-page bulletin, a copy of which was obtained by CNN, is titled "Al Qaeda Threat to Europe." 
 
 It says it was issued "to raise general security awareness and as part of our ongoing effort to provide information about any potential terrorist threat against the United States or our allies in Europe." 
 
 Japan issued a similar alert Monday, citing the warnings issued by the United States and by Britain, which raised the level highest for France and Germany. 
 
 On Friday, Sweden raised its threat level from "low" to "elevated," the third-highest threat level on a scale of five that ranges from "no threat" to "low threat" to "elevated threat" to "high threat" to "very high threat." 
 
 Several European governments said Sunday that they were not raising their already-high alert levels. The French Ministry of Foreign Affairs said Sunday that the U.S. advisory was "in line with the general recommendations that we have addressed to the French population." 
 
 "The indications provided by the U.S. authorities, in particular regarding terrorist threat in Europe are, of course analyzed, cross-referenced and where appropriate included in our national assessment of the threat, which still relies on a series of elements," the ministry said. "The terrorist threat remains high in France, the alert level remains unchanged at level red." 
 
 Britain's Foreign and Commonwealth Office changed its travel advisory for British citizens in France and Germany from a "substantial" threat of terrorism to a "high" threat, but the office said it does not comment on intelligence matters and thus could not say whether the change was related to the U.S. travel alert. 
 
 A spokeswoman for Germany's interior ministry said the country will remain at Level 2 alert, which indicates a "high, probable risk" of a terror attack. 
 
 Spain has remained at this stage since January of this year. 
 
 Over the weekend, CNN spoke with Sidiqi's sister in Hamburg, who said his family was shocked by the allegations against him. She said Sidiqi told his family in 2009 that he was traveling to Afghanistan to start a new life with his wife. They last heard from him shortly before his arrest, when he phoned to tell them that he would soon be returning home because he missed his family, said his sister, who described him as a devout, family-loving man. 
 
 German officials said the Hamburg group members were recruited from the Taiba mosque in Hamburg. In the 1990s, that same mosque -- then called Al Quds -- was attended by Mohamed Atta, who went on to become the lead hijacker in the 9/11 attacks. 
 
 A friend of Atta from those days has emerged as a crucial figure in the new plot, European intelligence officials tell CNN. Naamen Meziche, 40, a French citizen of Algerian descent, worked to persuade a number of young men praying at the Taiba mosque to join in jihad, the officials said. Though his exact whereabouts are unknown to authorities, he is thought to be in the Afghan/Pakistan border area. Meziche's wife told CNN that he was overseas. 
 
 According to a European counterterrorism official, Meziche had connections to al Qaeda dating to the 1990s that he rekindled once he arrived in Pakistan's tribal areas. 
 
 Most of the members of the group which coalesced late in 2008, left Pakistan before authorities had a chance to stop them, despite constant surveillance of suspected militants at the Taiba mosque, according to German intelligence officials. 
 
 The group used several routes to get to Pakistan, some going overland through Iran and some traveling by air via the Persian Gulf. Managing the logistics, according to German intelligence officials, was a man known as Asadullah M., 52, a Hamburg resident of Afghan origin who is thought to be in the Pakistani tribal area along the Afghan border. 
 
 Eight members of the travel group, including two wives of the militants, eventually made it to the tribal areas of Pakistan, where they joined the Islamic Movement of Uzbekistan (IMU), an Uzbek militant group with strong ties to al Qaeda, according to German intelligence officials. 
 
 One member of the group was Rami Makanesi, 25, a German of Syrian descent. Another was Shahab Dashti, a German citizen of Iranian descent. He appeared in an IMU video in late 2009. Wielding a knife and gun, he urged other Germans to join in jihad against American forces in Afghanistan. Several other Germans in the video were shown firing weapons in what appeared to be live-fire exercises. Several scenes featured what appeared to be the group's members using rockets and guns to practice storming enemy positions, honing the type of combat skills that Western counter-terrorism officials fear could be used in Western cities in a "Mumbai-style" attack. 
 
 In November 2008, more than 160 people were killed in an assault on hotels and other "soft targets" in Mumbai by members of Lashkar-e-Taiba, a terrorist group based in Pakistan. 
 
 One European counterterrorism official said Sidiqi told his interrogators that Meziche had assumed a planning role in the new reported plot -- assisted by Asadullah M. -- which Osama Bin Laden himself approved. Sidiqi said that Dashti, who appeared in the IMU video, was tasked to be a "foot-soldier" in the plot against Europe, a European counter-terrorism told CNN. German intelligence officials believe Dashti is still at large in the tribal areas of Pakistan. 
 
 Dashti, who previously followed a Western lifestyle, began attending the Taiba mosque after converting from Shia to Sunni Islam, in part, German intelligence officials said, to distance himself from a domineering father. Family members reached by CNN over the weekend said they believe he was tricked by extremists into going to Pakistan. His wife traveled with him to Pakistan and is still believed to be in the Afghan-Pakistan border region. 
 
 The imam of the Taiba mosque is Mamoun Darkazanli, a German businessman from Syria who was identified by the 9/11 Commission as having links to al Qaeda financiers. Spanish authorities charged him in 2003 with membership in al Qaeda, but as a German citizen he was not extradited. He faces no charges in Germany. Attempts by CNN to reach Darkazanli for a response on the latest plot have been unsuccessful. 
 
 In the years after 9/11 the Taiba mosque became a magnet for al Qaeda sympathizers across Europe. 
 
 "They all wanted to come and pray where Mohamed Atta prayed," a German intelligence official told CNN. 
 
 Hamburg authorities shut the mosque a few weeks after Sidiqi was arrested. 
 
 The decision to shut the mosque was difficult, said officials in Hamburg, because the presence in one place of so many militants made it easier to monitor their activities. But they said the mosque had become a recruiting center for jihadists across Europe. 
 
 Several militants now back in Germany who failed to make it to Pakistan's tribal areas are of continuing concern to members of German intelligence services, who have kept them under observation. 
 
 "Their greatest enemy is the United States," a German intelligence official told CNN. 
 
 A recent report by Hamburg's intelligence services said that 45 jihadists lived freely and openly in the city, from where they supported al Qaeda. High evidence thresholds under the German legal system have made it very difficult for authorities to make arrests, German officials told CNN. In addition to those actively supporting al Qaeda, another 200 Islamists living in the city are described as having "violent tendencies." 
 
 German intelligence officials told CNN that Hamburg, like many other European cities, faces a challenge from Islamist extremists, but that some cities, including London, face greater challenges. They said they are increasing resources to confront the problem of Islamist extremism. Radicalization, they said, is on the rise because of the growth of German-language extremist websites and the revolution in social media. 
 
 A senior German counterterrorism source told CNN that some 200 people have left the country since 9/11 to receive training with militant groups in the Afghanistan-Pakistan border region, and that dozens have returned. According to German intelligence officials, the uptick in U.S. drone strikes in the tribal areas of Pakistan has not staunched the enthusiasm of German militants wishing to travel there. 
 
 CNN's Claudia Otto and Homeland Security Correspondent Jeanne Meserve contributed to this story. ||||| An American missile strike killed five German militants Monday in the rugged Pakistan border area where a cell of Germans and Britons at the heart of the U.S. terror alert for Europe _ a plot U.S. officials link to al-Qaida leader Osama bin Laden _ were believed in hiding. 
 
 Soldiers prepare to patrol at Roissy Charles de Gaulle airport, Monday, Oct. 4, 2010. Japan issued a travel alert for Europe on Monday, joining the United States and Britain in warning of a possible terrorist... (Associated Press) 
 
 A soldier patrols at Gare du Nord train station in Paris, Monday, Oct.4, 2010. Japan issued a travel alert for Europe on Monday, joining the United States and Britain in warning of a possible terrorist... (Associated Press) 
 
 The sky is blue behind the TV tower in Berlin, Germany, Monday, Oct. 4, 2010. The TV tower is among the buildings in Berlin which are allegedly a target for terror attacks. U.S. authorities have issued... (Associated Press) 
 
 A police officer with a dog, patrols a central London train station, Monday Oct. 4, 2010. Britain's Foreign Office has upgraded its travel advice for France and Germany, warning Britons going to those... (Associated Press) 
 
 Tourists look at the Big Ben in London, Sunday, Oct. 3, 2010. The U.S. government has warned its citizens to be vigilant while travelling in Europe because of the threat of an al-Qaeda commando-style... (Associated Press) 
 
 Tourists pose with a guard at the Horse Guards Parade in London, Sunday, Oct. 3, 2010. The U.S. government has warned its citizens to be vigilant while travelling in Europe because of the threat of an... (Associated Press) 
 
 French soldiers patrol the area under the Eiffel Tower and walk past replicas for sale, in Paris, Sunday, Oct. 3, 2010. The State Department plans to caution Americans traveling in Europe to be vigilant... (Associated Press) 
 
 French soldiers patrol under the Eiffel Tower in Paris, Sunday, Oct. 3, 2010. The State Department plans to caution Americans traveling in Europe to be vigilant because of heightened concerns about a... (Associated Press) 
 
 Police officers watch the crowd at the Oktoberfest beer festival in Munich, southern Germany, Sunday, Oct. 3, 2010. The Obama administration is warning Americans about potential terrorist threats in Europe... (Associated Press) 
 
 Two tourists look a a map in Madrid Sunday Oct. 3, 2010. The State Department plans to caution Americans traveling in Europe to be vigilant because of heightened concerns about a potential al-Qaida terrorist... (Associated Press) 
 
 British police officers guard one of the entrances to the Houses of Parliament in central London, Monday Oct. 4, 2010. Britain's Home Secretary Theresa May said that the threat of terrorism in the U.K.... (Associated Press) 
 
 Police officers patrol through the crowd at the Oktoberfest beer festival in Munich, southern Germany, Sunday, Oct. 3, 2010. The Obama administration is warning Americans about potential terrorist threats... (Associated Press) 
 
 Tourists visit the Horse Guards Parade in London, Sunday, Oct. 3, 2010. The U.S. government has warned its citizens to be vigilant while traveling in Europe because of the threat of an al-Qaeda commando-style... (Associated Press) 
 
 Soldiers prepare to patrol at Roissy Charles de Gaulle airport, Monday, Oct. 4, 2010. Japan issued a travel alert for Europe on Monday, joining the United States and Britain in warning of a possible terrorist... (Associated Press) 
 
 Tourists mix with Spaniards in Madrid, Spain, Sunday Oct. 3, 2010. The State Department plans to caution Americans traveling in Europe to be vigilant because of heightened concerns about a potential al-Qaida... (Associated Press) 
 
 British police officers guard one of the entrances to the Houses of Parliament in central London, Monday Oct. 4, 2010. Britain's Home Secretary Theresa May said that the threat of terrorism in the U.K.... (Associated Press) 
 
 Tourists pose with a guard at the Horse Guards Parade in London, Sunday, Oct. 3, 2010. The U.S. government has warned its citizens to be vigilant while traveling in Europe because of the threat of an... (Associated Press) 
 
 Tourists pose by a telephone box by Parliament Square in London, Sunday, Oct. 3, 2010. The U.S. government has warned its citizens to be vigilant while traveling in Europe because of the threat of an... (Associated Press) 
 
 The attack, part of a recent spike in American drone strikes on Pakistan, came as Germany said it has "concrete evidence" that at least 70 Germans have undergone paramilitary training in Pakistan and Afghanistan, and about a third have returned to Germany. 
 
 Authorities across Europe have heightened security at airports and other travel hubs as well as at main tourist attractions following the U.S. warning of an al-Qaida-linked terror plot targeting London, Paris, Berlin and other European capitals. 
 
 Washington warned Americans over the weekend to use caution when traveling in Europe and imposed a curfew on some U.S. troops based in Germany. On Monday, Britain, Japan and Sweden issued warnings of their own, advising their citizens traveling in Europe to be on alert for possible terrorist attack by al-Qaida or other groups. 
 
 Police officers with sniffer dogs patrolled subways in Britain on Monday, while soldiers and mounted police were dispatched to two major churches in Paris _ Notre Dame in the heart of the city and Sacre Coeur on the Right Bank. Paramilitary troops were also seen patrolling the area around the Eiffel Tower _ twice evacuated in recent weeks for unspecified threats. 
 
 The U.S. missile strike in Pakistan killed five German militants taking shelter in a house in the town of Mir Ali in North Waziristan, a known hub for foreign militants with links to al-Qaida, Pakistani intelligence officials said. 
 
 The terror cell said to be behind the Europe plot _ eight Germans and a Briton _ were believed to have been in hiding in the region. A second Briton was killed in a U.S. strike last month. 
 
 A German Foreign Ministry spokesman said Monday that his office was checking the report of the latest killings. He declined to be named in keeping with policy. 
 
 However, the German police agency responsible for terrorism investigations, the Federal Criminal Police Office, said as many as 220 people have traveled from Germany to Pakistan and Afghanistan for paramilitary training, and at least 70 have received it. A Pakistani intelligence official last week said there are believed to be around 60 Germans in North Waziristan now. 
 
 Despite the growing evidence of a terror plot, France, Britain and Germany _ the nations believed to be the targets of the scheme _ have not changed their terror threat levels. On Monday, the German government played down the fears by declaring there is "no reason to be alarmist." 
 
 The threat is being viewed differently by Washington and European capitals, and some analysts said it was a matter of approach. Such differences have played out repeatedly in the years since the 9/11 attacks on the United States, they said. 
 
 British intelligence prefers to keep targets under surveillance as they plan attacks, often waiting until the final stages to intervene _ hoping to gather evidence and to gain information about contacts in Britain and overseas. 
 
 "That cuts significantly too close to the bone for the United States. They are not happy to let plots run for too long," said Tobias Feakin, director of national security and resilience at London's Royal United Services Institute, a military think tank. 
 
 In Germany, the homeland security spokesman for the main opposition Social Democratic party said there is a different security culture in Europe and the United States. 
 
 "After 9/11 there were almost daily warnings of new threats in the U.S. which _ thank God! _ never became a reality" in Germany, Dieter Wiefelspuetz said. 
 
 In Washington, State Department spokesman P.J. Crowley said Monday that the travel advisory was issued because of extensive evidence of a plot. 
 
 "We felt, having tracked intelligence over a lengthy period of time, it was appropriate to issue this alert at this moment," he said. 
 
 "We specifically have said continue with your travel plans, but just be cautious because we are aware of active plots against the United States, American citizens and other allies around the world." 
 
 German Interior Minister Thomas de Maiziere insisted his nation had no concrete evidence of an imminent attack. "There is no reason to be alarmist at this time," de Maiziere said. 
 
 He said he had spoken with U.S. Homeland Security Secretary Janet Napolitano about the travel advisory and that it is not "in keeping with our assessment of the situation." 
 
 In a rare public speech last month, MI5 director general Jonathan Evans warned that the risk of attacks can never be completely eradicated. 
 
 "We appear increasingly to have imported from the American media the assumption that terrorism is 100 percent preventable and any incident that is not prevented is seen as a culpable government failure. This is a nonsensical way to consider terrorist risk," Evans said. 
 
 Many tourists said they planned to be vigilant but would not change their plans. 
 
 "I'm very happy to be here in France. I think we're very safe, and I trust the French government to keep us safe," said James O'Connell, 59, of Pittsburgh. 
 
 Hannah Haskins, an 18-year-old from Portland, Oregon, who has been in Spain for a month working as an au pair, said she is headed to Britain next week for a visit and will be on guard but not obsessed with the terror alert. 
 
 "I probably will be alert and it is going to be high on my mind, but it won't change my plans," she said. 
 
 "I will catch the subways, go to the museums and enjoy. There are so many threats and this one is very vague. There is always a threat, so what's the difference?" 
 
 ___ 
 
 Associated Press writers Asif Shahzad in Islamabad, Paisley Dodds and David Stringer in London, Juergen Baetz in Berlin Shino Yuasa in Tokyo, Eileen Sullivan and Matthew Lee in Washington, Jorge Sainz in Madrid and AP Television News reporter Nicolas Garriga in Paris contributed to this report.
– An American missile attack has killed at least five German nationals suspected of being part of a terror cell training in Pakistan, Pakistani officials say. The missile hit a house in Waziristan, the region where authorities believe a terror cell training for an attack on Europe was hiding out, the AP reports. Dozens of European militants are believed to be training in the area and it's not clear whether the drone attack is linked to the terror plot that has Europe on alert. European intelligence officials say they believe a terror cell that originated in Hamburg is behind a plot to launch coordinated attacks on city centers, CNN notes. The group, whose members are of assorted ethnic backgrounds including Turkish and Iranian, attended the same Hamburg mosque as 9/11 hijacker Mohamed Atta. The group is believed to have left Hamburg to train in Pakistan early last year, officials say, citing intelligence gained from a German militant captured in Afghanistan in July.