Washington ( CNN ) -- The U.S. State Department has issued a travel alert for U.S. citizens in Europe , based on information that suggests that al Qaeda and affiliated organizations continue to plan terrorist attacks . Americans are warned to be aware of their surroundings and protect themselves when traveling . One senior U.S. official said earlier that in addition to the travel alert from the State Department , `` U.S. military installations are taking prudent precautions . This is a serious situation . '' A separate U.S. official said the alert is being prompted by the volume of intelligence on possible terror threats , rather than new intelligence . It emerged last week that U.S. intelligence officials were looking at information about a possible `` Mumbai-style '' attack in cities across Europe . A United Kingdom security source said Saturday that it was not believed the expected U.S. alert was a result of new intelligence received in the last few days . But the source added that the intelligence related to the possible Mumbai-style attack was being looked at very seriously on both sides of the Atlantic . The security source said there are no plans to raise the terror threat level in the United Kingdom from severe to critical . A severe threat level means an attack is considered highly likely ; critical means an attack is expected imminently . A possible backlash from the French burqa ban is considered a factor in the expected warning , the security source said . The French Senate recently approved a law banning veils that cover the face , including the burqa , worn by some Muslim women . Mumbai , the financial hub of India , was the site of a three-day terror attack two years ago that left more than 160 people dead . Ten men launched the carefully planned assault , targeting prominent sites such as the Taj Mahal Palace and Tower hotel , the Oberoi-Trident hotels , the historic Victoria Terminus train station and a Jewish cultural center . A U.S. law enforcement official told CNN Saturday that an advisory will likely be sent to law enforcement agencies around the United States after the travel alert is issued , `` just to keep them in the loop . '' But the official added that current intelligence is about Europe rather than a threat in the United States . CNN 's Elise Labott , Jeanne Meserve , Andrew Carey , Barbara Starr , Pam Benson and Carol Cratty contributed to this report .
NEW : State Department alert warns Americans in Europe to be aware of surroundings . The warning comes after a series of attacks on U.S. diplomatic facilities and the deaths of four American diplomats earlier this month. Alert comes in light of recent terror threat information .