PATNA, India (AFP) - An Indian express train ploughed into a crowd of Hindu pilgrims in the country's east on Monday, killing 35 and triggering a riot as angry crowds went on the rampage, officials said.

The pilgrims were crossing the tracks at a station in the state of Bihar when the interstate passenger train ran into them, injuring dozens, a senior police officer said.

"Until now we have information that 35 people have been killed in the incident and dozens are injured," S.K. Bharadwaj, an additional director general of police, who is overseeing security at the crash site, told AFP.

Crowds converged on the Rajya Rani Express, setting carriages on fire and ransacking Dharhara station, some 178 kilometres from the state capital Patna, local railway chief Arun Malik told AFP.

"Six carriages have been set on fire and the station has been ransacked by the mob. Our staff have fled the station fearing attacks," Mr Malik said.

A senior railways official said it appeared the pilgrims were not aware of the incoming express train.

"Two trains were already stationary on other tracks and the Rajya Rani Express was given permission to pass," Mr Arunendra Kumar, chairman of the national railway board, told reporters in New Delhi.

"The accident occurred because some people left the platform of the station and came on the tracks," Mr Kumar said.

He said he has received reports from officials on the ground that the angry mob has tried to attack the train driver, and medical teams are on site.

"We are getting information that the train has been damaged and some coaches have been set on fire," he said.

"We don't know the status of the other staff but the train driver has been injured by the mobs surrounding the train."

"We have rushed emergency medical teams to help those injured in this accident."

There are hundreds of accidents on the railways annually.

In 2012, a government report said that almost 15,000 people were killed every year crossing India's rail which it described as an annual "massacre" due to poor safety standards.

Pedestrians guilty of "unlawful trespassing" walk across the tracks at many unofficial crossing points, the report said, adding that about 6,000 of the deaths occur in the congested and frenetic city of Mumbai alone.

Attempts to stop people riding on the roofs of trains have largely failed, vehicles routinely drive around barriers at crossings and passengers are often seen hanging out of open doors in the carriages.

The data is not broken down, but a vast majority of these deaths are people falling from the open doors of carriages or being hit on the tracks, which are mostly unsecured.

One of India's worst rail accidents was in 1981 when a train plunged into a river also in Bihar, killing an estimated 800 people.