More prisoner exchanges are expected between Ukraine and pro-Russian rebels in the east – a day after the two sides swapped hundreds of captives.
Ukrainian officials say they are hoping that four soldiers will be freed. The number of militants due to be released has not been confirmed.
On Friday, Ukraine said 146 of its soldiers had been freed for 222 rebels.
Meanwhile, Ukraine froze vital bus and rail links with Crimea, its southern peninsula annexed by Russia in March.
Crimea has no land corridor to Russia, and relies on a ferry in the Azov Sea and flights from Russia.
The peninsula – which is also heavily dependent on Ukraine’s power supplies – has also seen blackouts in recent days.
Kiev says it has to limit supplies, because Ukraine itself is experiencing power shortages.
In a separate development, the world’s two largest credit and debit card companies, Visa and Mastercard, said on Friday they could no longer support bank cards being used in Crimea, following fresh US sanctions imposed this month.
The moves come ahead of the traditional holiday season in the region, when people travel to be with their families for New Year.
Russian media reported that a number of people in Crimea on Friday were unable to withdraw cash or pay for goods bought in local supermarkets.
Ukrainian President Petro Poroshenko’s spokesman said on Friday that Kiev expected four more of its soldiers to be released on Saturday.
Spokesman Vyacheslav Tsegolko wrote in a Facebook post that the soldiers “would be able to celebrate New Year and Christmas with their families”.
Ukraine – a predominantly Orthodox Christian country – celebrates Christmas on 7 January.
Friday’s prisoner exchange – the biggest since the conflict began in April – took place near the town of Avdiyivka, about 35km (22 miles) north of Donetsk.
Ukrainian and Russian media showed rows of men in civilian clothes standing on a road, supervised by armed men.
“They only just told us that this would happen,” freed Ukrainian soldier Artem Syurik was quoted as saying by the Associated Press news agency.
“I am looking forward to seeing my parents and wife. They do not know I am coming.”
Freed rebel fighter Denis Balbukov said: “I want to eat fried potatoes and talk to my relatives.”
But he added: “I will go back to fighting. It was all right once we were moved to the detention centre, but to begin with, they really tormented and roughed us up.”
Inconclusive talks were held this week in Minsk, Belarus, on ending the conflict in eastern Ukraine, which has claimed 4,700 lives.
Although fighting has lessened considerably, the conflict continues and more than 1,300 people have died since a truce was announced in September.
Ukraine accuses Russia of actively supporting the militants with Russian soldiers and heavy artillery.
The Kremlin denies this but says its regular forces are fighting in eastern Ukraine as volunteers.