Police scrambled through precarious rail tunnels deep underground on Friday to hunt for clues and retrieve bodies after suspected al-Qaida bombers killed more than 50 people in London rush-hour blasts the previous day.

The attacks - which ministers said bore the hallmarks of the Islamic militant al-Qaida network - were London's deadliest in peacetime and coincided with the Group of Eight (G8) summit of industrialized countries in Gleneagles, Scotland.

London Police Chief Ian Blair said more than 50 people were killed in the blasts and 700 wounded.

He said the final death toll was not yet known due to the dangers of reaching some of the underground blast sites - police had not yet reached one of the bombed cars since the surrounding tunnel was deemed too unsafe to enter. Police sources said there could be more than 10 bodies still trapped underground.

Blair said police would "bend every sinew" to find those responsible for the blasts.

Andy Hayman, of the London police specialist operations branch, said the bombs were believed to have contained about 4.5 kilograms of explosives and could have been carried onto the trains and bus in backpacks.

On Friday, the police chief Blair said there is no evidence to suggest that suicide bombers were behind the series of deadly blasts in London. "There is absolutely nothing to suggest that this was a suicide bombing attack although nothing at this stage can be ruled out," Blair said of the attacks on three underground trains.

He said that in the case of the double-decker bus blown up there was also no indication that a bomber deliberately set off an explosive device while on board the vehicle. "It may have been that, but it may have been a bomb left on a seat, it may have been a bomb that went off in transit," he said.

More bombs feared

Fears of more attacks kept commuters and markets jittery.

"We have to have... maximum consideration of the risk of another attack and that's why our total effort today is focused on identifying the perpetrators and bringing them to justice," Home Secretary Charles Clarke told BBC radio. He said investigators were examining a statement from the "Secret Group of al -Qaida's Jihad in Europe".

The e-mail statement by the previously unknown group said: "Our mujahideen have carried out a blessed invasion in London and here is Britain now burning with fear and terror ... We have repeatedly warned Britain and have kept our promise."

An Internet statement from another group, calling itself the "Organization of al-Qaida - Jihad in the Arabian Peninsula" praised the attacks and said Rome would be targeted next.

The blasts battered financial markets, but oil prices recovered to near US$61 on Friday. Analysts said the attacks were expected to have a limited impact on the global economy and oil demand.

Source: China Daily