KOLKATA - A freight train smashed into the rear of a stationary passenger train in India's West Bengal state on Monday, killing at least 15 people and injuring dozens, police said, in an accident that railway authorities blamed on a disregarded signal.

Media showed images of the pile-up, with containers from the goods train strewn nearby, and one carriage left nearly vertical after the accident, which comes just over a year after a signalling error caused one of India's worst rail crashes.

At least 15 bodies have been pulled from the mangled carriages, Abhishek Roy, a senior police official in the eastern state's district of Darjeeling, the site of the accident, told Reuters.

Nearly 30 people were injured and rescue teams from the police and national disaster response force were working with doctors and residents of the area to clear debris from the derailed carriages, Roy added.

The goods train hit the Kanchanjunga Express travelling to Kolkata, the capital of West Bengal, from the northeastern state of Tripura, driving three carriages of the passenger train off the rails.

It was not immediately clear how many passengers were on board at the time.

Rescuers used iron rods and ropes to work free one carriage of the passenger train that had been swept upwards to lodge on the roof of the freight train by the impact of the collision.

The dead included the driver of the freight train and a guard on the passenger train, Jaya Varma Sinha, the head of the railway board that runs the countrywide network, told reporters.

The accident happened after the driver of the freight train disregarded a signal and hit the rear end of the express train, Sinha added.

Rescue work has been completed, Sinha said, while authorities were working to restore traffic, although the damage had been less extensive than initially feared.

"The guard's compartment in the passenger train was badly damaged," he added. "There were two parcel vans attached ahead of it which reduced the extent of damage to passengers."

Nearby residents heard a loud crash and saw the pile-up upon going to investigate, several told the ANI news agency, in which Reuters has a minority stake.

Prime Minister Narendra Modi offered condolences on the loss of life in the accident and said Railway Minister Ashwini Vaishnaw was on his way to the site.

About 288 people died a year ago in the neighbouring state of Odisha, in India's worst rail crash in more than two decades, caused by a signal failure.

(Reporting by Subrata Nag Choudhary and Sudipto Ganguly, writing by Shilpa Jamkhandikar; Editing by Clarence Fernandez)