LONDON // A large-scale terror attack was aimed at British landmarks and public spaces, security officials said Tuesday as more details emerged and police searched the homes of 12 British suspects being held for questioning.
The men - whose ages range from 17 to 28 - were arrested Monday in the largest counterterrorism raid in nearly two years. At least five were of Bangladeshi origin.
Lord Carlile, the government's independent watchdog for terror legislation, said Tuesday the alleged plot appeared significant and involved several British cities, but he did not identify the targets. Police have up to 28 days to either charge the men or release them.
Possible targets that were scouted include the Houses of Parliament in London and shopping areas around the UK, according to a security official who spoke to The Associated Press on condition of anonymity because the investigation was ongoing.
The plot, however, was unconnected to a larger European plot uncovered in the fall involving a Mumbai-style shooting spree in cities across Britain, France or Germany, the official said. Monday's arrests were also unrelated to last week's suicide bombing in Sweden and the plot did not appear to be timed for the holidays, he said.
Scotland Yard Assistant Commissioner John Yates said police searches of the men's homes could take days, and officers were seen Tuesday removing computers from their homes. The men were arrested in the cities of London, Cardiff, Stoke-on-Trent and Birmingham.
European officials typically step up security around the holidays, but this year especially after a Nigerian man with explosives taped to his underwear tried to blow up a plane on Christmas Day last year as it approached Detroit.
Umar Farouk Abdulmutallab, who had studied in London, had boarded the Northwest Airlines flight to Detroit from Amsterdam. The 24-year-old is accused of trying to blow up the flight. A judge in a federal court in Detroit has entered a not-guilty plea on Abdulmutallab's behalf.
Italian officials were investigating whether an explosive device found in a subway car in Rome on Tuesday was terror-related.
Iraqi officials claimed last week that captured insurgents believed the Stockholm bombing was part of a series of Christmas season attacks.
Britain's terror alert has remained unchanged at "severe" while Germany upped its terror alert Nov. 17 in response to an increased threat from Islamic extremists. Berlin's Interior Minister Ehrhart Koerting said recently the threat has eased but said it was necessary to remain vigilant.
In October, the United States warned its citizens living or traveling in Europe to be wary after details emerged of a larger European terror threat.
Monday's raid, a joint operation by Britain's domestic spy agency MI5 and police, was the largest since April 2009, when 12 men were detained over an alleged al Qa'eda bomb plot in the northern city of Manchester. All were released without charge and ordered to leave Britain.
One, Abid Naseer, was later re-arrested at the request of the U.S., which says he was involved a plot to bomb the New York City subway. He is in jail awaiting extradition.
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.
Europe has been the target of numerous terror plots by Islamist militants. The deadliest was 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 trains and a bus.