LONDON - A European terrorist plot is still enough of a threat for the United States to keep its current travel advisory, the U.S. State Department's counterterrorism co-ordinator said Thursday.

The State Department advised American citizens living or travelling in Europe earlier this month to take more precautions following reports that terrorists may be plotting attacks on a European city, possibly a shooting spree or other type of attack similar to the deadly 2008 Mumbai attacks in India.

The U.S. travel advisory is one step below a formal travel warning advising Americans not to visit Europe. It drew some skepticism among U.S. allies, most notably Germany, who questioned whether the United States was overreacting.

"We don't view the current circumstances warrant rescinding the alert," said Daniel Benjamin, the U.S. counterterrorism co-ordinator. "We think the situation is pretty much the same."

Benjamin insisted the information was credible and had been gathered over several months from multiple sources. Some of the plot details came from Ahmed Siddiqui, a German citizen of Afghan descent captured by US troops in Afghanistan in July.

"That said, some of the specifics were absent, and we would have liked to have been more able to say what we were seeing," he said. "Because that wasn't there, we went out with the alert that we did. We tried to couch it as carefully as we could ... but we felt we had an obligation -- both an ethical one but also a legal one -- to warn American tourists that this was a concern."

Germany insisted when the alert was issued that it was based on old information and said there was no indication of an imminent terror warning within its territory. Interior Minister Thomas de Maiziere said the nation faced a "high level of abstract threat ... there is at present not need for alarm."

German opposition lawmakers, meanwhile, speculated that the real reason behind issuing the advisory was the upcoming U.S. elections.

"Different countries handle these things in different ways," Benjamin said. "The Germans neither have the legislation we do in terms of having to issue alerts, nor do they have the tradition of handling these things perhaps as publicly as we do."

France's terrorism threat is the highest it has been in years. Security has also been boosted at busy tourist sites like Notre Dame Cathedral and the Eiffel Tower in Paris. French authorities have recorded nine bomb alerts in the capital last month -- a threefold increase from a year earlier. No explosives have been found.

Britain's Foreign Office has also warned travellers to France and Germany of a high terror threat.

Benjamin said informing the public could ultimately keep people safer.

"We didn't tell anyone not to travel here (Europe)," he said. "But we really do believe that if you give people some ideas on how to behave -- what to do in their travelling -- they will be more aware of their surroundings and take precautions, and will therefore be more secure."

He said misinformation and leaks surrounding the plot had complicated the government's efforts, including reports that some tourist attractions had been targeted.

"We didn't talk about specific targets," such as Berlin's Alexanderplatz, which "was a complete invention of one particular broadcaster," he said, declining to go into specifics. "We didn't get into a lot of the nitty gritty particulars because of intelligence concerns."

Europe has been a target of numerous Islamic terror plots -- the deadliest being the 2004 Madrid train bombings, when shrapnel-filled bombs exploded, killing 191 people and wounding about 1,800.

A year later, suicide bombers killed 52 rush-hour commuters in London aboard three subway cars and a bus.

In 2006, U.S. and British intelligence officials thwarted one of the largest plots yet -- a plan to explode nearly a dozen trans-Atlantic airliners.

U.S. intelligence officials still view al-Qaida's senior leadership along the border of Afghanistan and Pakistan as "the most formidable single threat," but the overall threat is considerable given the proliferation of groups in Africa and the Middle East who are aligned with al-Qaida.

Benjamin said the evolving scope of threats was also a challenge.

"I think we have to go on the assumption that these groups are constantly trying to increase the range of practices they could employ and they need to show that they're active," he said. "There's no reason to think that they won't try doing smaller attacks (instead of) spectacular attacks as they find it difficult to do the big operations."