In one of the worst railway disasters in India, at least 233 people were killed and more than 900 injured when three trains collided one after another in a horrific sequence in Odisha's Balasore district, setting off a massive rescue and evacuation process, officials said on Saturday.

"Death toll rises to 233 in the Balasore Train Accident," Odisha Chief Secretary PK Jena tweeted.

The train crash happened near the Bahanaga Baazar station in Balasore district, about 250 km south of Kolkata and 170 km north of Bhubaneswar, around 7 pm on Friday, prompting the Railway Ministry to order a probe.

The inquiry into the train accident will be led by A M Chowdhary, Commissioner Railway Safety, South East Circle, the Indian Railways said in a statement. The Commissioner Railway Safety comes under the Ministry of Civil Aviation.

Several coaches of the 12864 Bengaluru-Howrah Superfast Express, on the way to Howrah, derailed and fell on adjacent tracks, an official said.

"These derailed coaches collided with the 12841 Shalimar-Chennai Central Coromandel Express and its coaches capsized too," he said.

A goods train was also involved in the accident as some of the coaches of the Coromandel Express, which was heading to Chennai, hit its wagons after getting derailed, he added.

More than 2,000 people gathered at the Balasore Medical College and Hospital in the night to help the injured, and many also donated blood.

Chief Secretary Jena thanked the volunteers who donated blood to the accident victims in their hour of need.

"Five hundred units of blood collected overnight here at Balasore. Nine hundred units in stock at present. This will help in treating the accident victims. I'm personally indebted & grateful to all the volunteers who've donated blood for a noble cause," Jena tweeted.

The railways announced an ex-gratia of Rs 10 lakh for the next of kin of the deceased, Rs 2 lakh for those grievously injured and Rs 50,000 for those who got minor injuries.

Prime Minister Narendra Modi too expressed his distress over the accident, and announced an additional ex-gratia of Rs 2 lakh for the next of kin of the deceased and Rs 50,000 for the injured from the PM's National Relief Fund (PMNRF).

"Distressed by the train accident in Odisha. In this hour of grief, my thoughts are with the bereaved families. May the injured recover soon. Spoke to Railway Minister @AshwiniVaishnaw and took stock of the situation. Rescue ops are underway at the site of the mishap and all possible assistance is being given to those affected," he tweeted.

The Odisha government issued helpline 06782-262286. The railway helplines are 033-26382217 (Howrah), 8972073925 (Kharagpur), 8249591559 (Balasore) and 044- 25330952 (Chennai).

Expressing concern over the accident, in which a large number of people from West Bengal were involved, Chief Minister Mamata Banerjee said she was monitoring the situation along with the chief secretary and other officials.

West Bengal Chief Secretary HK Dwivedi said the state was sending a team led by minister Manas Bhunia and MP Dola Sen to the spot.

So far, 18 long-distance trains have been cancelled due to the accident, which happened on the Howrah-Chennai main line in the Kharagpur division of the South Eastern Railway. PTI AAM/AMR/ASG SOM JRC CK.