From the Met Police:
"At approx 08:50 on 7.7.05 we were called to Aldgate LT stn to assist the City of London police and BTP regarding an incident on the underground system.
All of the emergency services are on scene.
This has been declared as a major incident.
Too early to state what has happened at this stage.
There have been further reports from multiple locations in London of explosions. It is too early to say what has caused these explosions.
Police are responding to reports from:
Edgware Rd
Kings Cross
Liverpool St
Russell Sq
Aldgate East
Moorgate underground stations.
Furthermore there has been a confirmed explosion on a bus in Tavistock Place.
The MPS, BTP, City of London Police are working together to ensure officers are deployed to each scene.
There have been reports of numerous casualties but it is too early to say numbers at this stage."
Source: The Met Police
The Met are asking everybody in Central London to stay put if you're not affected by the blasts.