(Reuters) - The death toll from the collision of two Indian passenger trains in Odisha state has surged to 288 and more than 850 are injured, a state government official told AFP on Saturday, making the rail accident the country's deadliest in more than two decades.

The death toll is expected to increase, state Chief Secretary Pradeep Jena said in a tweet.

Sudhanshu Sarangi, the director general of the fire department in Odisha, told Reuters that 207 bodies had been recovered so far.

Images from the scene showed rescuers climbing up the mangled wreck of one of the trains to find survivors. Videos shared on social media showed the arrival of several ambulances and people being pulled out of the upturned train coaches.

"I was there at the site and I can see blood, broken limbs and people dying around me," an eyewitness told Reuters by phone.

Hundreds of young people lined up outside a government hospital in Odisha's Soro to donate blood.

Rescue teams have been mobilised from Odisha's Bhubaneswar and Kolkata in West Bengal, federal Minister for Railways Ashwini Vaishnaw said in a tweet late on Friday.

Three National Disaster Response Force teams are at the site of the accident, and six more teams are being mobilised, the country's National Disaster Response Force said.

The collision occurred at about 7pm local time (1330 GMT) when the Howrah Superfast Express, running from Bangalore to Howrah, West Bengal, derailed and became entangled with the Coromandel Express, which runs from Kolkata to Chennai, railway officials said.

Odisha Chief Minister Naveen Patnaik said authorities' priority was "removing the living to the hospitals".

Rescue operations were underway at the site and "all possible assistance" was being given to those affected, Prime Minister Narendra Modi said in a tweet.