Ukraine and Russian-backed rebels swapped hundreds of prisoners in the war-torn east of the country yesterday, one of the largest such exchanges since the outbreak of an insurgency almost four years ago.

The swap of captives on a dusty road close to the town of Gorlivka, 40 kilometres (25 miles) northeast of the rebels' stronghold of Donetsk is an attempt to revive a tattered peace deal between the Kiev army and rebels from the self-proclaimed Donetsk and Lugansk People's Republics.

The war in the former Soviet republic broke out in April 2014, after Russia annexed Crimea the previous month.

The conflict has already claimed more than 10,000 lives. A series of truce deals has helped lower the level of violence but did not end the bloodshed.

In the first exchange since September 2016, the Russian-backed eastern militia handed over to Kiev some 70 prisoners, officials from both sides said. The Ukrainian side for its part was releasing 250 rebels and their supporters.

The figures were significantly less than previously declared ones as dozens of prisoners -- largely from the Ukrainian territory -- have refused to move to the other side.

Two Ukrainians -- a man and a woman -- also opted to stay on the rebel side.

The prisoners massed at the exchange point with their belongings, shivering in zero temperatures, before boarding buses after their names had been called out.

Some of the detainees expressed relief after spending long months, and even years, in captivity.

"I was in captivity for two years," said reputed historian Igor Kozlovskiy, 63, who was captured by Donetsk rebels in suspicion of storing weapons.

"Still a lot of prisoners remain (behind bars in Donetsk)," the exhausted man in a red sweater and sport jacket told AFP minutes before he was handed over to the representatives of Ukraine.

The swap on the eve of the New Year and Orthodox Christmas holidays was agreed following negotiations involving Russian President Vladimir Putin and Ukraine's leader Petro Poroshenko.

"President Poroshenko personally coordinated all the work of all our relevant departments," lawmaker Iryna Gerashchenko, one of Ukraine's peace negotiators, said before the exchange.

The swap is in line with the so-called Minsk agreements brokered by Germany and France in 2015.

The last prisoner exchange between Ukraine and Russian-backed rebels took place in September 2016 when two pro-Kiev detainees were swapped for four separatist fighters at a checkpoint outside the rebel-held city of Lugansk.

Unusually, Russian Orthodox Patriarch Kirill helped mediate the talks on Wednesday's prisoner exchange, and three Russian priests were present.

"I hope that the process that has begun will continue and will guarantee the establishment of a just and long-lasting peace," he said on Monday.