Updated

The newest Olympic city went from a scene of triumph to a triage area.

Still euphoric over its big victory to host the 2012 Summer Games (search), London was hit by a series of deadly explosions Thursday that rocked its subway, tore open a packed double-decker bus and created chaos during morning rush hour. More than 300 were injured in what Prime Minister Tony Blair (search) called a series of "barbaric" terrorist attacks.

The jubilation in Trafalgar Square (search) on Wednesday following the Olympic vote contrasted with the looks of horror on the faces of casualties and witnesses after three explosions ripped through underground stations and one struck a bus in quick succession.

A day earlier, London had won the right to stage its first Olympics since 1948. Led by two-time Olympic gold medalist Sebastian Coe (search), the English capital beat long-time favorite Paris in the vote by the International Olympic Committee in Singapore.

When Londoners awoke Thursday to start the seven years of planning and construction, they were instead hit by the news of explosions in central London. The euphoric mood changed dramatically as people came to terms with the blasts.

"This was not a terrorist attack against the mighty or the powerful, it is not aimed at presidents or prime ministers, it was aimed at ordinary working-class Londoners," London Mayor Ken Livingstone said from Singapore before heading home.

Jubilation in the British camp in Singapore quickly turned to distress.

"It's terribly unfortunate in terms of timing," said Keith Mills, chief executive of London's bid team. "And clearly, our celebrations as a result of yesterday will have to be put on hold. Our thoughts go out to the families who've been effected. I hope that the security forces can get to the bottom of this quickly."

IOC president Jacques Rogge (search), who was informed of the attacks during the committee's annual general assembly in Singapore, sent messages of condolence and support to British officials.

"It is a sad fact of society today that tragic and shocking attacks of this nature can happen in any city at any time," the IOC said in a statement.

IOC spokeswoman Giselle Davies stressed the decision to award the games to London was not in question. London won the IOC vote, beating Paris, New York, Madrid and Moscow.

"From what we understand, this is not at all related to the Olympic Games," Davies said in Singapore. "We have full confidence in the London authorities in securing the event."

British Olympics Minister Tessa Jowell said celebrations planned to coincide with the return of the London 2012 delegation would be canceled. She declined further comment.

The explosions occurred while leaders of the G-8 summit, which included Blair, President Bush and six other leaders, was about to begin in Scotland. Blair said he would leave the summit at Gleneagles to return to London.

"Whatever they do, it is our determination that they will never succeed in destroying what we hold dear in this country and in other civilized nations throughout the world," Blair said.

Sports events scheduled in London for Thursday were called off, but a one-day international cricket match between England and Australia in Leeds and the Scottish Open golf tournament in Luss went ahead.

Formula One's British Grand Prix is expected to race as scheduled, with qualifying starting Saturday and the race Sunday at Silverstone.