Bomb attempts rattle London after 7/7

Areas of London are evacuated after the British capital sees four minor explosions - possibly detonators - on the metro system and on a bus...

The Reuters news agency says a nail bomb exploded at Warren Street tube station at about 1330.

Witnesses on the platform at Warren Street tube station told reporters they heard gunfire and saw smoke coming from a train.

Scotland Yard has confirmed it has deployed armed police officers to University College Hospital, which is next to Warren Street tube station.

The hospital is reported to be under lockdown and Sky News reports staff there have received a memo asking them to look out for a suspected bomber who is thought to be in the immediate area.

Police report no fatalities and one injury in Thursday's attacks.

Prime Minister Tony Blair has urged people to get on with their business as normal.

Speaking at Downing Street he said: "We know why these things are done. They're done to scare people."

'Not chemical'

London Underground has shut down Warren Street, Oval and Shepherd's Bush tube stations in a code Amber alert.

Emergency personnel entered Warren Street station wearing chemical protection suits, but found no chemical or biological traces, police said.

Police have confirmed there has been no trace of chemical components following an investigation at Oval station.

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

At Shepherd's Bush Hammersmith and City line station, police told reporters that a man had threatened to blow himself up and then ran off.

A route 26 bus in Hackney Road in Bethnal Green was also thought to be involved in an explosion and buildings around the bus have been visibly damaged. The area has been evacuated.

More bombs?

Eye-witness callers to rolling news channels are being told to hang up by police. They fear phone signals at the various incident scenes could detonate further bombs.

Reports say the explosions that have occurred so far are more likely to be the detonators of bombs, rather than the bombs themselves.

A COBRA (Cabinet Office Briefing Room A) meeting has been called at 10 Downing Street attended by Prime Minister Tony Blair, Metropolitan Police Commissioner Sir Ian Blair and representatives of foreign intelligence, MI6, and domestic intelligence, MI5.

Sir Ian Blair has appealed to Londoners to "stay where you are" in what he described as a "very serious incident".

The Metropolitan Police issued an appeal to people at work in Central London not to leave their offices for home until further notice.

"At this time we ask that all personnel remain in their place of work and DO NOT try to make their way home until advised so to do by ourselves," the statement said.

Two weeks ago, 56 people were killed and over 700 injured when four 10lb bombs were detonated at various locations on the London metro and on a bus.