LONDON – Police increased their guard around Buckingham Palace and other landmarks Wednesday as security officials monitored what they described as a fledgling terror plot to wage Mumbai-style shooting sprees or other attacks on Britain, France or Germany.
At least some of the recent CIA strikes in Pakistan were aimed at al-Qaida operatives suspected in the plot, U.S. officials said. European officials said the plot was still in its early stages and not considered serious enough to raise the terror threat level.
Still, the Eiffel Tower in Paris was briefly evacuated Tuesday — the second time in two weeks because of an unspecified threat — and French police were on alert.
A heavy police presence was seen Wednesday around Buckingham Palace, Trafalgar Square and Big Ben. Victoria Station was briefly evacuated after an unusual smell was reported.
"This plot was in its embryonic stages," a British government official told The Associated Press, speaking on condition of anonymity because of the sensitivity of his work. He said the plot had preoccupied the security community more than other recent threats, but did not merit changing the security threat level from severe to critical.
Some details about the plot came from Ahmed Siddiqui, a German citizen of Afghan background who was captured in Afghanistan in July, a U.S. official said.
Intelligence authorities used National Security Agency wiretaps to flesh out details, U.S. officials said, and while a Mumbai-style shooting spree was one possibility, there was no concrete plan. The officials spoke on condition of anonymity because they were not authorized to speak about the plot.
Secretary of State Hillary Rodham Clinton told reporters Wednesday the U.S. was working closely with its European allies, but declined to provide specifics.
"We are not going to comment on specific intelligence as doing so threatens to undermine intelligence operations that are critical in protecting the United States and our allies," Clinton said. "As we have repeatedly said, we know that al-Qaida and its network of terrorists wishes to attack both European and U.S. targets."
"I want Americans to know how focused we all are in the government and how committed we are not only in protecting our own country but in protecting our friends and allies."
The Department of Homeland Security would not say Wednesday whether U.S. security has been enhanced as a result of the terror threats in Europe.
Revelations of the plot came just ahead of the anniversary on Thursday of the publication of the Prophet Muhammad cartoons in a Danish newspaper.
It also came as Spanish authorities announced they had arrested an American citizen of Algerian origin on suspicion of financing al-Qaida's North African affiliate.
Mohamed Omar Debhi, 43, was taken into custody Tuesday, although Spain's Interior Ministry said the arrest was not connected to the terror threat. He is suspected of laundering money and sending some of it to an associate in Algeria, Toufik Mizi, to be passed on to al-Qaida cells in the Islamic Maghreb, an Algerian terror group.
Europe has been a target of numerous Islamic terror plots — the deadliest being the 2004 Madrid train bombings, when 10 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.
Despite the beefed up security presence at tourist sites in London and other European capitals on Wednesday, most visitors took the news in stride and went on with their sightseeing.
"In this case, ignorance is bliss," said Theodore John, a 35-year-old banker from Pittsburgh who was visiting Buckingham Palace and heard about the threat Wednesday.
Officials gave no other details of the terror plot except to say that it originated in Pakistan with a group "threatening to wage a Mumbai-style attack" on cities in Britain, France and Germany.
"This was the headline threat but it was not clear whether the attack would come in the form of shootings or other small-scale attacks," said the British government official.
A three-day siege in 2008 by gunmen in the Indian city of Mumbai left 166 people dead and raised fears of similar low-budget types of attacks around the world — a departure from the sophisticated and precision-planned Sept. 11 terror attacks in the United States in 2001.
U.S. intelligence had heard of the European plot about a month ago and was monitoring the people involved, according to two U.S. officials. The CIA recently stepped up airstrikes from unmanned aircraft in northern Pakistan, in part to disrupt the plot.
However, a second British government official said that while the drone strikes were thought to have disrupted the planning of the attacks, the operation was still considered active. He spoke on condition of anonymity because of the sensitivity of his work.
The Obama administration has intensified the use of drone-fired missiles in Pakistan's border area. This month there have been at least 21 attacks — more than double the highest number fired in any other single month.
CIA director Leon Panetta was in Pakistan for talks with the head of the country's main spy agency. A Pakistani intelligence officer confirmed Panetta was meeting Wednesday with Lt. Gen. Ahmed Shuja Pasha.
A Pakistani official said some information about the plot was coming from a suspect who had been interrogated at the military prison at Bagram Air Base near Kabul. Siddiqui is reportedly being held in Bagram.
The Pakistani official, who spoke on condition of anonymity because the investigation was continuing, characterized the evidence as more aspiration than a fully planned terror plot.
Associated Press writers Angela Charlton in Paris, Daniel Woolls in Madrid, Gillian Smith and David Stringer in London, Kimberly Dozier in Islamabad and Matt Apuzzo, Adam Goldman, Eileen Sullivan and Matt Lee in Washington contributed to this report.