DEFIANT Londoners returned to the Tube and the buses today, determined to carry on with their lives the day after terrorists brought carnage to the capital.

Although there were fewer commuters than usual, hundreds of thousands of people made their daily journeys into a city which still bore the scars of yesterday's co-ordinated terror attacks.

As the capital prepared to mark the 60th anniversary of the end of the Second World War this weekend, there was the same resolve that life would go on - whatever the terrorists had hoped to achieve.

A huge manhunt is under way to find the bombers, who killed more than 40 people during 56 minutes of hell which terrorised the capital.

Home Secretary Charles Clarke said all efforts were being concentrated on catching the bombers, to stop them striking again.

He said: "The number one purpose is to identify the perpetrators and arrest them.

"There is obviously a danger if there is a group that has committed these attacks not brought to justice and therefore able to continue thinking about further attacks.

"That is, of course, the number one preoccupation the police and security services have at this moment," he added.

Mr Clarke said the Government was taking seriously a claim on a website from an al Qaida group that it was responsible.

The Home Secretary defended the decision to lower the level of security threat in the capital before the attacks, saying that all the security services thought the risk had got "slightly lower".

"Obviously, it was wrong," he said. "We have looked very carefully at the threat we are now under, particularly in the light of events yesterday, and the threat level will be increased."

He agreed that the authorities had "absolutely no idea" yesterday's attacks were being planned.

But he denied claims that London's security had been compromised because of Metropolitan Police officers being at the G8 summit in Scotland.

Prime Minister Tony Blair, who has vowed that the culprits will be brought to justice, was expected to return to London later today after the final session of the G8 summit in Gleneagles.

Anti-terrorist detectives are investigating the possibility that Britain was subjected to its first suicide bombing after the series of co-ordinated, no warning strikes in the centre of London.

A passenger on the double- decker bus ripped apart in one of the four blasts said he saw an "extremely agitated" man rummaging in a bag just seconds before the explosion.

Police put the confirmed death toll at 37, but that looked set to rise with 95 seriously injured among the 300 casualties taken to hospital.

Police sources said more than 40 people had died and Australian Prime Minister John Howard told reporters in Canberra that the death toll was 52.

* The Queen and the Prince of Wales were today visiting people caught up in the bomb tragedy.

Scotland Yard said there would be an increased visible police presence across the capital today.

Extra patrols were to include officers from the Met, City of London Police and British Transport Police.

* Scotland Yard has issued a casualty hotline number, 0870 1566 344.