But amid the chaos eyewitnesses reported that a packed double decker bus in the Russell Square area had been severely damaged in a blast.
Scotland Yard confirmed the bus explosion and said it was dealing with 'multiple explosions'' in London.
A second bus was damaged in Tavistock Square.
Describing the Russell Square blast, eyewitness Belinda Seabrook said she saw an explosion rip through the bus as it approached the Square.
'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,' she said.
Mrs Seabrook said the bus was travelling from Euston to Russell Square and had been 'packed' with people turned away from Tube stops.
'It was a massive explosion and there were papers and half a bus flying through the air, I think it was the number 205,' she said.
'There must be a lot of people dead as all the buses were packed, they had been turning people away from the tube stops.
'We were about 20 metres away, that was all.'
The blasts plunged the capital into chaos as world leaders gathered in Scotland for the G8 summit.