Ukraine government forces and pro-Russian separatists have exchanged dozens of prisoners captured during fighting in eastern Ukraine, as part of a cease-fire agreement signed earlier this month.
Ukrainian President Petro Poroshenko said 36 servicemen were released early on September 12. He said 21 others had been released the day before.
Ukrainian forces handed over 31 rebels.
The prisoner exchange took place outside Donetsk, one of two separatist-held provincial capitals in eastern Ukraine.
Hundreds of people are believed to have been detained by both sides since the start of the conflict in April.
The two sides have repeatedly accused each other of delaying prisoner exchanges and violating the September 5 cease-fire deal.