MINSK, Belarus (AP) — Four Ukrainian nationals on Friday were released after spending years in separatist captivity and handed over to the Ukrainian government in a rare gesture of good will.

The prisoner release, originally announced on Thursday, was completed on Friday when the four men were handed over to Ukrainian officials at the airport in the Belarusian capital, Minsk. They looked tired but had no visible signs of mistreatment or torture.

Three of the four men are Ukrainian military and each of them spent from one to four years in captivity.

"We're very grateful for our release to everyone who helps the peace," said 55-year old Eduard Mikheyev, who spent two years in captivity. "We thank everyone who has been praying for us."

Hostilities between Russia-backed separatists and Ukrainian government troops in eastern Ukraine have killed more than 13,000 people since 2014. Prisoner exchanges between the warring parties became increasingly rare. The last one was carried out in 2017.

Friday's prisoner release was arranged by Viktor Medvedchuk, a Ukrainian oligarch with strong ties to Russian President Vladimir Putin. Speaking at Minsk airport, Medvedchuk blamed the Ukrainian government for not doing enough to encourage more prisoner exchanges.

The men were released in the separatist-controlled east, taken across the border to Russia and then flown to Belarus where they were met by Ukrainian officials.

The separatist leaders described the release as a goodwill gesture and expressed hope that it will lead to an exchange of more prisoners held by both sides.

The separatists say that Kiev holds about 100 of their forces in captivity while the Ukrainian government estimates that about 50 of its military personnel are held prisoner in the east.

Ukrainian Presider Volodymyr Zelenskiy, who earlier this week called on Putin to release all the Ukrainians held in separatist captivity, dismissed Medvedchuk's mediation efforts as electioneering. Medvedchuk's party is running for parliament in the next month's snap elections and is currently polling second after Zelenskiy's party.

Copyright 2019 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.