At least 288 people have been killed and more than 850 injured in a three-train collision in India, officials said, the country's deadliest rail accident in more than 20 years.

Images from the crash site showed smashed train compartments torn open with blood-stained holes near Balasore, in the eastern state of Odisha.

Carriages had flipped over entirely in the crash late yesterday and rescue workers searched for survivors trapped in the mangled wreckage, with scores of bodies laid out under white sheets beside the tracks.

As dawn broke today, rescue workers were able to see the full extent of the carnage.

Prime Minister Narendra Modi reached the scene, talked to the rescue workers and inspected the wreckage.

He is likely to visit hospitals and see the survivors.

Sudhanshu Sarangi, director general of Odisha Fire Services, said that the death toll stood at 288.

The Ministry of Railways said it has initiated an investigation into the incident

"The rescue work is still going on," he said from the accident site, adding there were "a lot of serious injuries".

India is no stranger to railway accidents and has seen several disasters, the worst of them in 1981, when a train derailed while crossing a bridge in Bihar and plunged into the river below, killing between 800 and 1,000 people.

But yesterday's crash is believed to be the worst since the 1990s.

Odisha state's chief secretary Pradeep Jena confirmed that about 850 injured people had been sent to hospitals following the crash, which took place around 200km from the state capital Bhubaneswar.

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

Train carriages were flipped over by the impact of the crash

Amitabh Sharma, executive director at Indian Railways, said that two passenger trains "had an active involvement in the accident" while "the third train, a goods train, which was parked at the site, also got (involved) in the accident".

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

With so many injured, the injured were carried by both ambulances and buses to any hospital that had space.

SK Panda, a spokesperson in Jena's office in Odisha state said "all big government and private hospitals from the accident site to the state capital" were prepared to support the injured.

The spokesperson added that authorities had sent "75 ambulances to the site and had also deployed many buses" to transport injured passengers.

Rescuers are searching for survivors

At Bhadrak District Hospital, ambulances brought in casualties, with the bloodied and shocked survivors receiving treatment in crowded wards.

Mr Vaishnaw said that he was rushing to the accident site, with rescue teams including the National Disaster Response Force and air force working frantically.

"Will take all hands required for the rescue ops," he said on Twitter.

Nepal's Prime Minister Pushpa Kamal Dahal offered his "deep condolences" in "this hour of grief".

US State Department spokesman Vedant Patel said: "Our thoughts are with the people of India at this time."

Despite the latest crash, railway safety, thanks to massive new investments and upgrades in technology, has improved significantly in recent years.

President Michael D Higgins has written to the President of India, Droupadi Murmu, to express his sympathies following the horrific train crash in Odisha state.

The Tánaiste, Micheál Martin expressed his "deepest sympathies" and offered his condolences to those who lost lost loved ones in the collision.

"Deepest sympathies to the people of India after the devastating accident in Odisha yesterday.

"I would like to send sincere condolences to all those whose loved ones were lost in the train crash. Our thoughts are also with the survivors," Mr Martin tweeted.

Pope Francis has voiced immense sadness and offered his prayers and condolences after yesterday's three-train collision.

"Entrusting the souls of the deceased to the loving mercy of the Almighty, (Pope Francis) sends heartfelt condolences to those who mourn their loss," senior Vatican cardinal Pietro Parolin said in a telegram published by the Holy See.

"His Holiness likewise offers prayers for the many injured and for the efforts of the emergency service personnel," said the telegram, which was addressed to the apostolic nuncio in India, Leopoldo Girelli.