LONDON (AFP) - Police found a second explosive device in London Friday hours after defusing a car bomb, putting the capital on high alert two days after a new government was formed, a senior source told AFP.
The new device was found in Park Lane, the security source said, after police spent hours searching a suspicious vehicle in an underground car park following the discovery of a car bomb in the city's Haymarket entertainment district the night before.
Asked about a BBC report that a second device had been found, the source told AFP: "That is correct," adding that the device was not supposed to explode in Park Lane, where the car had been taken to a car pound.
"It is not the area where it was meant to detonate," the source said, adding that it was supposed to have gone off somewhere near Haymarket, where the first bomb was found.
The Metropolitan police said it would hold a press conference at 1945 GMT where a statement would be read out. It gave no further details.
Speaking before the second device was found, new Prime Minister Gordon Brown said the alert was a fresh warning of the threat faced by London, which next week marks the second anniversary of suicide attacks which killed 52 people.
The head of Scotland Yard's counter-terrorism unit Peter Clarke would not speculate on who was behind the bomb -- comprising gas cylinders, petrol and nails -- found outside a nightclub on Haymarket near Piccadilly Circus.
But he said: "Even at this stage it is obvious that if this device had detonated, there could have been significant injury or loss of life."
Rajeshree Patel, who was in the Tiger Tiger club when it was evacuated, told BBC television: "I think there would have been a lot of fatalities. There were approximately 500 people inside Tiger Tiger at the time."
As the United States praised the British authorities for their swift action, Clarke said police had no warning of an attack and it was unclear if the nightclub was the target but there were similarities with previous plots.
Members of an Islamist-inspired gang were jailed for life earlier this year after plotting to attack a number of high-profile British targets, including London's Ministry of Sound nightclub.
And a Muslim convert was put behind bars for 30 years here last November for plotting devastating attacks in London and New York, including a plan to detonate limousines packed with explosives at key landmarks.
A security source quoted by the Press Association news agency said it was "entirely possible" the latest incident had overseas links as insurgents in Iraq had used similar methods, but they were keeping an open mind.
The alerts provided a baptism of fire not just for Brown, but also for his Home Secretary Jacqui Smith, who was less than 24 hours into the role.
She met Brown in Downing Street and afterwards called for public vigilance.
"We are currently facing the most serious and sustained threat to our security from international terrorism," she said.
Smith earlier chaired a meeting of the government's emergency contigencies committee, COBRA, and reported to Brown's senior ministers at an extended cabinet meeting.
The first bomb was discovered by chance -- Clarke said an ambulance crew treating a person at Tiger Tiger called in police explosives experts after noticing a metallic green Mercedes car giving off smoke just before 02:00am (0100 GMT).
Inside they found "significant quantities" of petrol and a "large number" of nails, he added.
Police sources said there was as much as 60 litres of petrol on the back seat of the car and in the boot (trunk).
A hunt was on for the driver with detectives expected to scour footage from closed circuit television cameras in streets surrounding Haymarket, which is busy with revellers into the early hours of the morning.
The alert came days ahead of the second anniversary of the July 7, 2005 attacks on London's public transport system that killed 56 people, including four Islamist suicide bombers.
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