Sky keeps adding eyewitness accounts:

"It's chaos, with people trying to work out what has happened," said a spokesman.

One witness said the packed underground train he was on was 200 metres from King's Cross when there was a huge flash.

The train stopped and people were using umberellas to smash windows of the trains. Passengers were led out of the train by underground staff.

London Underground Tube Diary reports:

listen to the radio or keep clicking on Google news for the lastest but the whole of the London Underground has been closed. Completely unprecedented in my memory.

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