LONDON - Detectives hunted Saturday for suspects who abandoned two explosives-packed cars in the heart of London's nightlife district, reviewing closed circuit television footage and scouring the vehicles for clues.
Counterterrorism officers at Scotland Yard briefed Prime Minister Gordon Brown on Saturday, and the British leader later chaired a meeting of top spies, police and senior officials in COBRA, the government's emergency committee, his office said.
Detectives said they were keeping an open mind about the suspects, but terrorism experts said the signs pointed to a cell linked to or inspired by al Qaeda. Police would not comment on an ABC News report saying police had a "crystal clear" picture of one suspect from CCTV footage.
Police said they were strengthening patrols in the city to reassure the public, with 350 officers on duty at the annual Gay Pride parade through central London, not far from where two Mercedes loaded with gasoline, gas canisters and nails were found Friday.
One car was abandoned outside a nightclub on Haymarket, a busy street of shops, clubs, theaters and restaurants just yards from Trafalgar Square and Piccadilly Circus.
The other had been towed after being parked illegally on a nearby street and was discovered in an impound lot about a mile away near Hyde Park.
Deputy Assistant Commissioner Peter Clarke, the Metropolitan Police anti-terrorism chief, said the two devices could have caused "significant injury or loss of life."
The plot was uncovered a week before the second anniversary of the July 7 suicide bombings that killed 52 commuters on the city's transit system.
"London on the Edge" said the front-page headline in The Independent newspaper while the Daily Mail wondered, "Where's the Next Bomb?"
Mayor Ken Livingstone urged Londoners to remain vigilant.
"The discovery of two potential car bombs in central London, with those responsible still at large, means we face a very real threat of terrorist attack at this moment in time," he said.
The Times newspaper reported that police distributed a document to nightclubs two weeks ago warning of the threat from "vehicle-borne explosive devices" -- car bombs. The document, prepared by the National Counterterrorism Security Office, took the form of general counterterrorism advice for British clubs.
Terrorism experts said the improvised devices discovered Friday were similar to ones used by homegrown terror cells -- including the bombs used in the July 7 attacks -- although the discovery of the second device suggested a coordinated and more sophisticated attack, possibly a terror cell with links to al Qaeda in Pakistan.
Intelligence officials were examining a post to an Islamist website -- hours before the cars were found -- that suggested Britain would be attacked for awarding a knighthood to the novelist Salman Rushdie and for intervening in Muslim countries.
The U.S.-based SITE Intelligence Group, which monitors extremist websites, said a post on the al-Hesbah forum asked, "Is London craving explosions from al Qaeda?" and added, "I say the good news, by Allah, London will be hit."
SITE said the message had been posted to an unmoderated, public section of the forum, and its relationship, if any, to the car bombs could not be verified.
U.S. Rep. Peter King, R-N.Y., was briefed on the investigation and confirmed British authorities had found a cell phone.
"They found a cell phone, and it was going to be used to detonate the bomb," King said Friday.
Police would not comment on the claim.
Clarke said police were examining footage from closed-circuit TV cameras, hoping the surveillance network in central London would help them track down the drivers of the Mercedes.
The CCTV footage will be compared with license plate recognition software, he said.
There had been no prior intelligence of planned al Qaeda attacks, a British government official told The Associated Press on condition of anonymity because of the sensitivity of the investigation.
A British security official said the domestic spy agency MI5 would examine possible connections between the bomb attempt and at least two similar foiled plots -- to attack a London nightclub in 2004, and to pack limousines with gas canisters and shrapnel.
In the 2004 plot, accused members of an al Qaeda-linked terror cell were convicted of plotting to blow up the Ministry of Sound nightclub, one of London's biggest music venues.
