The BBC News website is covering events as they unfold:

1055 A doctor tells Reuters there are at least 90 casualties at Aldgate station

1053 Home Secretary Charles Clarke makes a statement outside Downing Street about "dreadful incidents" causing "terrible injuries". He says Prime Minister Tony Blair has been informed and advises the public in London not to make unneccessary journeys

1049 Police say there are serious casualties, but no deaths are confirmed, Associated Press reports

1025 The BBC's Andrew Marr, with the prime minister in Gleneagles, says Number 10 is "still unsure" whether the explosions are a terrorist attack

1023 confirmed explosion on a bus in Tavistock Place

1021 Scotland Yard reports "multiple explosions" in London, the Press Association reports

1014 An eyewitness tells PA that a bus has been ripped apart in an explosion in central London

1009 Witness Christina Lawrence, who was on a train leaving Kings Cross, tells BBC News 24: "There was a loud bang in the tunnel and the train just stopped and all of a sudden it was filled with black, gassy smoke and we couldn't breathe"

1002 Scotland Yard says it is dealing with a "major incident"

0940 British Transport Police say power surge incidents have occurred on the Underground at Aldgate, Edgware Road, King's Cross, Old Street and Russell Square stations

0933London Underground reports "another incident at Edgware Road" station, PA reports

0933 Passengers are told that all London Underground services are being suspended because of a power fault across the network, PA reports

0924 British Transport Police say the incident was possibly caused by a collision between two trains, a power cut or a power cable exploding. Police report "walking wounded"

0915 Press Association reports emergency services called to London's Liverpool Street Station after reports of an explosion