Four explosions hit London underground system and bus on Thursday, causing at least one injury but no death had been reported yet.

Three London tube stations were cleared and three underground lines were shut down after minor explosions took place.

Police cordoned off large areas around Warren Street, Oval and Shepherd's Bush Tube stations in Eastern London after smoke coming from two of the stations.

The whole of the Northern Line has been suspended, along with the Victoria Line and the Hammersmith and City.

British Transport Company said one man was injured at Warren Street station where reports said a nail bomb exploded .

An eyewitness at Oval station said there had been a small bang, and a man had then run off when the Tube reached the station. 

"We all got off on the platform and the guy just ran and started running up the escalator," one witness who gave her name as Andrea told the BBC.

"Everyone was screaming for someone to stop him. He ran past me ... and he ran out of the station. In fact he left a bag on the train," she said.

A blast blew out the windows of a bus in Hackney in east London, but there were no reported injuries.

"The bus driver heard a bang at the back of the bus. He thought it was probably a vehicle that had hit him," a Reuters report quoted a police officer as saying.

"He stopped at a nearby bus stop and saw a suspect package at the back of the bus," he said.

The blasts came exactly two weeks after more than 56 people were killed and over 700 people injured in blasts on underground railway trains and a bus in London.

(Xinhua News Agency, Chinadaily.com via agencies July 22, 2005)