Two commuter trains carrying an estimated 1,300 passengers between them collided shortly after 0800 GMT at Clapham Junction - Europe's busiest railway junction.

A third empty train later ran into the wreckage killing some passengers who had survived the first crash.

Surgery at the scene

Many passengers are still trapped as fire crews are cutting through the tangled carriages to reach them.

Emergency services have said the extent of the injuries mean some passengers have received operations at the scene.

At nearby St George's Hospital in Tooting staff are on emergency alert as coaches and ambulances wait to take those needing medical care to its new accident and emergency unit.

Passengers well enough to leave by foot, stood by the rail track and were described as "visibly shocked and distressed".

Many have been taken to a nearby school for first aid treatment.

Witnesses, unable to reach survivors because of the extent of the wreckage, have reported seeing appalling injuries.

They described how carriages were sent hurtling into the air before crashing back down again after the collision.

'Signalling failures'

The accident took place when the 0718 from Basingstoke to Waterloo approached the junction.

Early reports indicate it was slowing for signals when the 0614 from Poole, travelling from Bournemouth due to track problems, ran into the back of it.

Experts have said this train would have been travelling at about 40mph.

Shortly afterwards an empty train leaving Clapham junction hit the wreckage.

British Rail has said initial reports indicate the crash was caused by signalling failures.

The Transport Secretary Paul Channon is understood to be on his way to the scene of the tragedy.

Prime Minister Margaret Thatcher has promised a full public inquiry.


In Context

The Clapham rail crash was the worst train accident of recent times.

The Hidden inquiry into the crash recommended the installation of automatic train protection (ATP) for the whole rail network.

The ATP equipment governs the speed of trains and automatically stops them at red lights.

But the �750m price tag was considered too high by British Rail and the government, immediately prior to privatisation in 1993.

In 1998 after the Paddington rail crash Deputy PM John Prescott said "money was no object" in upgrading railway safety systems.

An inquiry led by Lord Cullen into fatal crashes at Southall in 1997 and at Ladbroke Grove in 1999 once again called for ATP to be installed by 2010 on the railways.

But in 2002 the Transport Secretary, Stephen Byers, said the government would not commit to the �3bn needed to install ATP.