Three London Underground stations were evacuated following unspecified incidents, London police said this evening. In addition, the Archway and Moorgate stations were cleared.

"We can confirm that emergency service personnel are responding to reports of incidents at three locations on the London underground system,'' police spokeswoman Kirsten Ross said.

Three Underground lines have been suspended -- the Victoria, Northern and Hammersmith and City lines, the spokeswoman said.

A British Transport Police spokesman said: "One person has received an injury at Warren Street. "We cannot confirm what the injury is, how it was received or who serious it is. We are still waiting for more information."

Some witnesses said they heard gunshots at Warren Street and saw an assailant running from the scene but Scotland Yard sources said it was unclear if the noise was from gunfire or detonating caps.

Panicking passengers

A passenger on a tube train about to arrive at Warren Street tube station said another passenger had told him there had been an exploding rucksack. He described seeing smoke and dozens of panicking passengers running through the train.

The news follows a series of terrorist attacks that rocked the city on July 7, two weeks ago, killing 56 people. Police have identified four men they say were bombers in the incidents earlier this month. All of them died in the explosions.

Sky News also reported there was an incident on a bus in east London, without citing anyone