A series of al Qaeda-based threats to attack American and Western targets in Europe , as well as threats to launch attacks inside the United States , has caused significant concern inside the U.S. intelligence community , CNN has learned . Officials are trying to determine the extent to which the threats may be linked and determine what it may mean about the strength of al Qaeda in several countries . While the `` threat stream '' has evolved during the past six months , according to a senior U.S. official , none of the threats has been corroborated . The official said the threats appear to detail `` a lot of activity where intelligence suggests there are operational cells , '' but so far , `` we do not see operational cells of al Qaeda inside the United States , '' the official said , although he emphasized it could not be ruled out . U.S. officials as well as analysts have long said they believe al Qaeda is focused on attacking outside the United States because of the difficulty in penetrating U.S. homeland security . But these latest threat streams suggest domestic U.S. targets also continue to be looked at by al Qaeda . Worry No . 1 : Al Qaeda in the Arabian Peninsula . One of the biggest concerns right now remains efforts by Yemen-based al Qaeda in the Arabian Peninsula to attack inside Yemen , in Europe and inside the United States . The U.S. Embassy , which was closed several weeks ago , is now expected to remain closed for several more days because of a `` credible threat stream , '' a second senior U.S. official told CNN . While it 's believed AQAP is mainly focused on targeting inside of Yemen , officials say an attempt to attack inside the United States or to recruit others to carry out such an attack can not be ruled out . Worry No . 2 : Core group in Pakistan . Separately , still another official confirms to CNN that the core al Qaeda group in Pakistan is also seeking to place operatives in places to attack U.S. targets overseas and domestically . U.S. officials confirm an operative who uses the code name Abdullah al-Shami , who is living in Pakistan , may now be heading that group 's efforts to plan external attacks . The New York Times first published al-Shami 's name in February and noted that U.S. intelligence believes he was born in the United States but moved to the Middle East as a child . The New York Times reported that as an American-born citizen , al-Shami could be a target for attack by a U.S. drone . U.S. officials refused to comment , but a private sector analyst who has followed the matter in detail told CNN that killing al-Shami had been discussed in the past . If al-Shami indeed is activity pursuing attacks against the U.S. , it would indicate that the core al Qaeda group in Pakistan might be resurgent in its capabilities . Worry No . 3 : Spillover effects from Syria . The third threat stream continues to come from Syria . U.S. officials tell CNN they believe 70 or more Americans have traveled to Syria to fight , and many may have returned home along with other fighters with Western passports . Over the past several months , the U.S. has sought to closely track all Americans traveling to Syria . Earlier this month , the Treasury Department imposed sanctions on an alleged al Qaeda operative , Abd Al-Rahman Muhammad Zafir Al-Dubaysi Al-Juhni . Treasury said that in 2013 , he was part of a group of senior al-Qaeda members in Syria formed to conduct external operations against Western targets . It 's also believed Al-Juhni was in Pakistan at some point , putting him in a position to have interacted with al-Shami .
A `` threat stream '' from al Qaeda groups has evolved during the past six months . The threats target Europe as well as the United States . Official to CNN : So far , `` we do not see operational cells of al Qaeda inside the United States '' Al Qaeda in the Arabian Peninsula , based in Yemen , is of particular concern .