Four people were killed and dozens injured when a passenger train derailed at high speed.

The 12.10pm London King's Cross to Leeds GNER service came off the line at Hatfield in Hertfordshire today (Tuesday), ripping apart the buffet car.

Emergency services said at least 19 people were seriously injured with about 80 walking wounded. Witnesses described scenes of "mayhem" with bodies by the track and people crying.

Casualties were being taken to the Queen Elizabeth II Hospital in Welwyn Garden City, with the Lister Hospital in Stevenage on standby.

A Channel Four News reporter Justin Rowlatt, who was a passenger on the train, told ITV News: "The roof has been completely ripped off the restaurant car. There is a guy with a broken leg still inside the train and two people with severe gashes. The first class carriages have completely come off the rails."

Another passenger, Stephen Morgan, said of the aftermath: "Mayhem. The only thing I could say is mayhem ... there were ladies crying and everything."

A Railtrack spokeswoman said the two coaches had derailed when the train was close to the line speed of 115mph for that section of track.

Transport Minister Lord Macdonald praised the emergency services and said his thoughts were with the families of those who had died. He had asked the HSE to provide an "urgent" report on the crash.

In June 1998, another high-speed GNER train derailed on the same track just 20 miles away, slightly injuring nine people, the Health and Safety Executive said.

An emergency helpline was set up for worried friends and relatives on 08459 441551.