The chief executive of London's [Images] successful bid team for the 2012 Olympics [Images] said on Thursday his delegation was devastated by the news of a series of explosions on London's transport system.

Keith Mills said the London team, who defeated Paris in Wednesday's International Olympic Committee vote, had cancelled all celebrations planned for later in the day.

"We are devastated, completely and utterly devastated," he told reporters.

"It's our town, our city. We're praying for the people who have been affected."

Police and transport officials said several people were killed and many injured in the blasts, which caused chaos during the morning rush hour in the British capital.

London mayor Ken Livingstone, part of the bid team, was due to fly back to London later on Thursday. He rushed past reporters without speaking and went to his hotel room after hearing the news while in a taxi as he returned from a shopping trip.

Mills said he did not believe the blasts were connected to the London Olympics. "It's a terrible coincidence," he said.

"It just shows that no city is safe at the moment. It's a terrible tragedy."

Mills said a farewell ceremony at the airport for his delegation had been called off because of the news.