Ukraine and pro-Russian separatists in eastern Ukraine are due on December 27 to complete their exchange of prisoners.
Ukrainian news agency UNIAN said 146 of the planned 150 Ukrainian government troops were handed over on December 26.
UNIAN said the remaining four should be handed over on December 27.
Ukrainian President Petro Poroshenko met with the recently released servicemen at a military air base early December 27 telling them "as president, and as an ordinary citizen, my heart is filled with joy that you…will be able to greet the New Year with your families."
Ukrainian authorities were supposed to deliver 220 separatist gunmen. It was unclear if all of those people were exchanged on December 26.
State security sources in Kyiv said the separatists would still be holding about 500 government soldiers after the exchange.
Based on reporting by UNIAN and Interfax