|Police forensics officers load a Mercedes car said to have contained a potentially viable explosive device onto a lorry in Haymarket in central London (AFP Photo)|
Police made safe a suspected car bomb in central London on Friday and new Prime Minister Gordon Brown said the alert, near the anniversary of a major attack, shows the "serious and continuous" threat faced by Britain.
There was widespread disruption across the centre of the capital because of the suspected bomb in the Haymarket, in the heart of London's Theatre district.
Police said they were called to the suspiciously parked car just before 2:00am (0100 GMT).
"They discovered what appeared to be a potentially viable explosive device. This was made safe," said a police statement.
Police later said the car contained gas cylinders.
One unnamed eyewitness told Sky News that door staff at a nightclub on Haymarket alerted police after a large silver saloon car was driven erratically before smashing into bins outside a foreign currency exchange bureau.
The driver then left the scene.
The alert was raised ahead of the second anniversary of the July 7, 2005 attacks in London that killed 56 people, including four Islamist suicide bombers.
"The first duty of a government is is the security of the people," said Brown, just two days into the job after taking over as prime minister from Tony Blair.
"And as the police and security services have said on so many occasions, we face a serious and continuous threat to our country."
Defence Secretary Des Browne told BBC radio: "It does appear to be a very serious incident."
The alert, in a zone normally packed with tourists, theatre-goers and revellers, brought heavy traffic congestion to the heart of London's West End and disruption on the London Underground.
A blue tent covering what is believed to be the car was in place behind police tape and what appeared to be plain clothes police were present.
New Home Secretary Jacqui Smith chaired a meeting of the government's emergency contigencies committee "COBRA". Smith was to report to Brown's cabinet.
"This incident does indicate the need for us to be vigilant at all times," Brown said.
"I will stress to the Cabinet that the vigilance must be maintained over the next few days."
Britain has been on the second highest level of security alert -- "severe" -- since the British Islamist extremist bombers detonated homemade bombs on three Underground trains and a bus two years ago.
Two of the bombers justified the actions because of Britain's involvement in Iraq, where three British soldiers were killed in a roadside bomb attack Thursday.
The domestic intelligence service MI5 said a "severe" threat level means there is a "serious and sustained threat from international terrorism to the UK and UK interests overseas".
MI5 said on its website: "The most significant terrorist threat comes from Al-Qaeda and associated networks."
There is also threat from the spread of weapons of mass destruction.
But an unnamed intelligence source, quoted by Britain's domestic Press Association news agency, said: "All options, including the Irish, are open at this stage."
Britain's new Justice Secretary Jack Straw told BBC radio that the government had been quickly informed of the alert.
Straw, a former home and foreign secretary, whose time in the latter post was dominated by the Iraq war, declined to comment further. "It's really for the police to make statement when they judge the time is right."