NOTE: This is a developing story and details will be added as they become available.

LONDON - Near simultaneous explosions rocked the London subway and tore open a double-decker bus during the morning rush hour Thursday, causing at least two deaths and dozens of injuries in what Prime Minister Tony Blair said was a "barbaric" terrorist attack timed to disrupt the Group of Eight summit.

The explosions came a day after London was awarded the 2012 Olympics and as the G-8 summit was getting under way in Scotland.

"We are concerned that this is a coordinated attack. We are aware that one of the sites does contain indications of explosives," London police chief Sir Ian Blair said on Sky News.

He said authorities had not received any warning. "We have been at a very high state of alert. Of course if there had been any kind of specific warnings we would have dealt with it," he said.

"There have been a number of dreadful incidents across London today," said Home Secretary Charles Clarke, Britain's top law enforcement officer. He said there were "terrible injuries."

Police confirmed two deaths and said there were at least six explosions.

Blair said he was leaving the G-8 summit in Scotland for the day to return to London, while the other leaders continued the meeting.

One witness, Darren Hall, said some passengers emerging from an evacuated subway station had soot and blood on their faces. He told BBC TV that he was evacuated along with others near the major King's Cross station and only afterward heard a blast.

Buses destroyed
Sky News showed a picture of a mangled red bus; police said they suspected a bomb caused the explosion.

Police confirmed an explosion destroyed a double-decker bus at Russell Square in central London, and Dow Jones Newswires reported police reporting explosions on at least two others buses.

A witness at the Russell Square blast said the entire top deck of that bus was destroyed.

"I was on the bus in front and heard an incredible bang, I turned round and half the double decker bus was in the air," Belinda Seabrook told Press Association, the British news agency.

She said the bus was packed with people.

"It was a massive explosion and there were papers and half a bus flying through the air," she said.

'Walking wounded'
Police said incidents were reported at the Aldgate station near the Liverpool Street railway terminal, Edgware Road and King's Cross in north London, Old Street in the financial district and Russell Square in central London, near the British Museum.

London Ambulance Service said several vehicles had been dispatched to the area near Liverpool Street station.

"We believe there was some sort of explosion. There are some walking wounded at Aldgate," said a spokesman for City of London police, speaking on condition of anonymity. "We are not sure of the scale of the incident. Reports are still coming in."

Bradley Anderson, a subway passenger, told Sky News that "there was some kind of explosion or something" as his train reached the Edgware Road station in northeast London. "Everything went black and we collided into some kind of oncoming train," Anderson said.

Simon Corvett, who was on an eastbound train from Edgware Road station, said: "All of sudden there was this massive huge bang."

"It was absolutely deafening and all the windows shattered," he said. "There were just loads of people screaming and the carriages filled with smoke.

"You could see the carriage opposite was completely gutted," he said. "There were some people in real trouble."