Ukraine and Russian-backed rebels have swapped hundreds of prisoners in the war-torn east of the country, 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 on Wednesday was 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 73 prisoners over to Kiev. The Ukrainian side released 233 rebels and their supporters, officials from both sides said.

The figures were significantly lower than previously declared, as dozens of prisoners -- almost all 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 historian Igor Kozlovskiy, 63, who was captured by Donetsk rebels on suspicion of storing weapons.

"Still a lot of prisoners remain (behind bars in Donetsk)," he told AFP minutes before he was handed over to the representatives of Ukraine.

Hundreds of people turned out at Kiev airport late Wednesday to welcome home the released prisoners, waving national flags, bouquets of flowers and shouting "Glory to Ukraine! Glory to our heroes!"

"Hello sweetie. You see, Daddy came back," one soldier said over the phone to a child as his weeping wife hugged him tightly, after 21 months held captive by separatists.

- 'Thanks for your stamina' -

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.

In his comment immediately after the exchange was completed, Poroshenko hailed the persistence of the Ukrainian soldiers.

"I have just thanked our lads who are coming back from captivity. Thanks for your stamina, guys," he said on Facebook.

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

German foreign minister Sigmar Gabriel greeted the long-awaited exchange as "an important step in the implementation of the Minsk agreements", urging the sides to conduct further steps to fulfil the peace deal.

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.

The head of the separatist self-proclaimed Donetsk People's Republic, Alexander Zakharchenko, thanked the patriarch for his involvement.

"People who have spent more than three years in captivity will be able to return home thanks to the church and the authorities," he said.

On Wednesday, the Ukrainian army reported the death of one soldier in the renewed fighting, the first combat casualty after the latest Christmas ceasefire came into force Saturday.

Ukraine and its Western allies accuse Russia of funnelling troops and arms across the border.

Moscow has denied the claims despite overwhelming evidence that it has been involved in the fighting and its explicit political support for the rebels.