The Ukrainian military and pro-Russian separatist groups, which have been battling for years in eastern Ukraine, exchanged hundreds of prisoners on Wednesday ahead of the new year.

The transfer of 237 prisoners from the Ukrainian government side and 73 from the rebel side was the largest since the conflict erupted in 2014 in Ukraine's two eastern-most regions, which border Russia.

In the first major prisoner exchange in months, separatists from the self-proclaimed Luhansk People's Republic bused 16 captives to the no-man's land while Ukrainian government representatives delivered 99 people.

The sides had agreed to exchange more prisoners, 306 and 74, but dozens decided to stay on Ukrainian state-held territory and one decided to remain with the rebels, the Interfax news agency reported.

Ukrainian President Petro Poroshenko met prisoners after the exchange and thanked them for their service to their country, according to a statement on his Facebook page.

The previous day, Poroshenko met prisoners' families, describing the exchange as a "symbol of our struggle and victory."

"Nothing is more important than to return our people home," he said, according to an official transcript.

The swap between the Kiev army and rebels from the self-proclaimed pro-Russian republics took place close to the town of Gorlivka, 40 kilometers (25 miles) northeast of the rebel stronghold Donetsk.

A simmering conflict in eastern Ukraine between Russia-backed separatists and government troops has killed more than 10,000 since 2014. A truce signed in 2015 stipulated an exchange of all prisoners but both sides are believed to keep dozens, if not hundreds, captive for use as bargaining tools.

Separatist leaders and a Ukrainian government representative agreed on the prisoner exchange last week with the mediation by the head of the Russian Orthodox Church. Ukraine is supposed to release 306 people, and the separatists 74.