Officers were called to the Haymarket area, after an ambulance crew responding to a call about an injury at a nearby nightclub noticed smoke coming from a car parked in front of the club.
A bomb squad was called to the scene and disabled the bomb.
Early photographs of the silver Mercedes showed a canister bearing the words "patio gas" indicating it was propane gas, next to the car. The back door was open with blankets spilling out.
|"We are currently facing the most serious and sustained threat to our security from international terrorism" |
British interior minister
The car was later removed from the scene.
Peter Clarke, Britain's anti-terror police chief, said the explosives were powerful enough to have caused "significant injury or loss of life," possibly killing hundreds.
Jacqui Smith, the UK's new interior minister, called an emergency meeting of officials, calling the attempted attack "international terrorism."
"We are currently facing the most serious and sustained threat to our security from international terrorism," she said.
"This reinforces the need for the public to remain vigilant to the threat we face at all times."
Clarke said police plan to examine footage from closed-circuit televison cameras in the area, hoping the surveillance network that covers much of central London will help them track down the driver of the Mercedes.
The discovery came hours after Gordon Brown, the British prime minister, named a cabinet to succeed Tony Blair.
"The first duty of a government is the security of the people and as the police and security services have said on so many occasions we face a serious and continued security threat to our country," Brown, in his third day in office, said.
Security around parliament was stepped up, with police body-searching drivers of vehicles entering the area.
A large area near Piccadilly Circus, packed with tourists, theatres, restaurants and pubs, was sealed off after the car was found.
Office workers unable to enter their buildings to start the work day milled outside, watching the police operation.
The bomb alert came almost two years after a series of coordinated suicide bomb attacks on London's transport network killed 52 commuters, the first suicide bombings in Western Europe.