Police in East Anglia today warned the public to be extra vigilant following the finding of a massive car-bomb in central London today.A Mercedes packed with petrol, nails and gas canisters was found outside a nightclub in the heart of the West End in the early hours of this morning.

Police in East Anglia warned the public to be extra vigilant following the finding of a massive car-bomb in central London today.

A Mercedes packed with petrol, nails and gas canisters was found outside a nightclub in the heart of the West End in the early hours of this morning.

Police said it was a large device which was potentially moments away from killing a "significant number' of people. There were at least 60 litres of petrol on the back seat and in the boot of the car in various sized containers.

Deputy Assistant Commissioner Peter Clarke, head of Scotland Yard's counter-terrorism command, said: "It is obvious that if the device had detonated there could have been significant injury or loss of life."

Whitehall sources said that the police and security services were looking at possible international links - including similarities to improvised car bombs used by insurgents in Iraq.

“It is entirely possible. There are various things - it is outside a nightclub, it is a vehicle-borne device, it is close to the anniversary of the July 7 attacks. But we are keeping an open mind,” one source said.

Today Mark Hopkins, Assistant Chief Constable of Cambridgeshire police, said: "There is nothing to suggest any connection with Cambridgeshire.

“There is no need for alarm, but we would ask people to take the commonsense precautions to be expected in these situations.”

A Suffolk police spokesman said every officer in the force was being briefed about the car bomb.

“We are aware of the incident in London,” he added. “At this stage, there is no intelligence to link it to Suffolk. However, as a precautionary measure, police officers and police community support officers have been briefed about the incident and told to be extra vigilant while out on patrol in the community.”

Prime Minister Gordon Brown said the incident showed that Britain faced a “serious and continuous threat' and the public “need to be alert” at all times.

He said: "I will stress to the Cabinet that the vigilance must be maintained over the next few days.'

Speaking in her first full day in the job, Home Secretary Jacqui Smith said: "What I think is very important is that the public remain vigilant at all times.

"Obviously the police are investigating and I think we should allow them to get on with that without undue speculation.'

A police cordon was thrown around the Haymarket, causing massive disruption to thousands of rush-hour commuters.

Forensic officers supervised the removal of the metallic light-green Mercedes saloon in a covered transporter lorry.

The alert came almost two years since four suicide bombers brought carnage to London's transport network, claiming the lives of 52 innocent people on July 7.

The current threat level for terrorism in the UK, set by MI5, is classed as "severe', one level lower than the highest "critical'.

Security experts said the bomb could have been timed to coincide with the change at the top of Government.

Michael Clarke, Professor of Defence at King's College London, said whoever was behind the intended attack would have left a lot of information at the scene which would help police track them down.

He said security services would now be concerned that the bomb may be part of a wider plot, and that there could be other devices planted around the capital.

"Any car coming into central London would be on a lot of surveillance footage. Also nobody can make a bomb without leaving behind a lot of DNA.'

He urged anyone with information to ring a confidential hotline number 0800 789 321.