The BBC's Asit Jolly describes the scene of the crash

The accident happened when a train, the Frontier Mail, from Delhi to Amritsar left the rails at Khanna, near the city of Ludhiana early on Thursday morning.

The BBC's Mike Wooldridge reports from New Delhi

A few minutes later, another train travelling in the opposite direction from Jammu to Sealdah crashed into the de-railed carriages.

Reports say many of the victims were in the front four cars of the moving train.

Trapped in wreckage

Officials are already calling it the worst railway accident in India for three years.

At one point about 1,000 railway workers and others were helping search and free travellers trapped in the wreckage.

A BBC correspondent who visited the scene of the crash, Asit Jolly, says the death toll is almost certain to go up.

He says that spilt diesel fuel is hampering rescue work because it is posing a fire risk, preventing rescuers from using gas cutting equipment.

A full investigation is underway, although there is no suspicion of foul play or sabotage at this point; officials suspect the two trains had been wrongly dispatched on the same line.

Emergency services and local people look for survivors

The BBC's Delhi correspondent, Daniel Lak, says India has one of the world's largest railway networks, with almost 13 million people travelling by train every day.

Accidents are surprisingly infrequent, he says, given the size of the network but when they do occur there's often a large number of casualties because of overcrowding.