Two weeks after the deadly bomb attacks in London, the British capital has been targeted by a new series of explosions.
Three bombs went off on the London transport system, while at least one other device failed to detonate, police said. One person was injured.
Minor explosions occurred on two Underground trains and a bus, leading to part of the rail network being closed down on Thursday.
Prime Minister Tony Blair called for calm.
London police chief Ian Blair said the incidents were "clearly very serious" although the blasts appeared to be smaller than those which occurred in the capital two weeks ago.
He said it appeared that some devices had not gone off properly.
Police were called out to three central London stations: Warren Street, Oval and Shepherd’s Bush. Large areas around the stations were cordoned off.
One person was slightly injured at Warren Street.
The whole of the Northern Line was suspended, along with the Victoria Line and the Hammersmith and City line.
In the east of the city an explosion blew out the windows of a bus. The driver reported no injuries.
The incidents were reported at lunchtime on Thursday, exactly two weeks after four bomb blasts in the London transport system, which killed 56 people.
swissinfo with agencies
On Thursday June 7, three bombs exploded on or close to the London Underground and a bus was blown up.
The terrorist attacks caused 56 deaths and injured around 700.