A train collision in India's eastern Odisha state killed at least 120 people and injured 850 others on Friday.

According to Odisha State Disaster Management Authority, the incident took place after a passenger train collided with a goods train in the state's Balasore district on Friday evening.

"We have more than 120 deaths per the last count and the number is increasing as there are a lot of serious injuries, head injuries," Sudhanshu Sarangi, director general of Odisha Fire Services, told AFP from the accident site.

"A very sad incident and the prognosis is not good."

Odisha state's chief secretary Pradeep Jena confirmed that "about 850 injured people have been sent to hospitals," with rescue work ongoing.

"Our top priority now is rescuing (the passengers) and providing health support to the injured," he said.

The country's Prime Minister Narendra Modi tweeted: "Distressed by the train accident in Odisha. In this hour of grief, my thoughts are with the bereaved families. May the injured recover soon."

Anil Kumar Mohanty, a medical officer in Balasore, told AFP that they have rushed doctors and medical staff to the accident site.

One survivor told local TV news reporters that he had sleeping when the accident happened, and woke to find himself trapped under around a dozen fellow passengers, before somehow crawling out of the carriage with only injuries to his neck and arm.

Another TV station showed graphic images of a train car toppled to one side of the track, as residents tried to pull victims to safety.