British Home Secretary Charles Clarke warned Sunday that the terrorists who hit London on Thursday could be planning more attacks in Britain, the Sky news reported.

"Our fear is, of course, of more attacks until we succeed in tracking down the gang that committed the atrocities on Thursday. That is why the No. 1 priority has to be the catching of the perpetrators," said the secretary, who was "very optimistic" of catching the bombers.

Meanwhile, detectives revealed that the three bombs on London subway trains had exploded almost simultaneously at 8:50 a.m. on Thursday.

Previously police had believed that the bombs went off over a period of 26 minutes but technical data from London Underground showed there was a gap of only about 50 seconds between the first and third explosions.

The bomb on a double-decker bus in central London, which killed 13 people, went off almost an hour later at 9:47 a.m.

Police are scrutinizing hundreds of hours of close-circuit television footage in a bid to trace the London bombers.

The confirmed number of deaths from the four blasts is 49, but the figure is expected to rise significantly with at least 20 bodies still trapped in the wreckage deep below ground in the tube station.

The Abu Hafs al-Masri Brigade has claimed responsibility for the attacks in the name of al-Qaida. The grouping also claimed responsibility for the Madrid bombings which left 191 people dead.

Source: Xinhua