DONETSK, Ukraine - Ukrainian authorities and pro-Russia rebels exchanged nearly 370 prisoners Friday, a major step toward easing hostilities in eastern Ukraine.

Ukraine handed over 222 prisoners and the rebels released 145 people, according to Russia's state RIA Novosti news agency - the biggest one-time prisoners swap since the pro-Russian insurgency flared up in eastern Ukraine in April.

The Interfax news agency quoted Svyatoslav Tsegolko, a spokesman for Ukrainian President Petro Poroshenko, as saying that 146 Ukrainian prisoners were released Friday and four more would be freed Saturday. The figures corresponded to an earlier Ukrainian official statement, which said 150 Ukrainian prisoners were to be released.

Hundreds of others were released in previous months.

Numbers of those to be released varied Friday, and tensions were flying high as buses carrying the prisoners arrived at a site north of the main rebel stronghold of Donetsk.

At some point during the exchange, separatist-rights ombudsman Darya Morozova was quoted by Tass news agency as saying the exchange was pushed back until Saturday.

Russia's state television showed Ukrainian war prisoners boarding buses in the main rebel stronghold of Donetsk before being driven to a location north of the city where the exchange took place.

On the site where the swap was conducted, prisoners were called up by groups of 10, with officials from both sides verifying their identities.

The exchange had been tentatively planned for earlier in the week.

On Thursday, the leader of the breakaway People's Republic of Donetsk, Alexander Zakharchenko, told reporters that no headway had been made during a Wednesday session of the negotiations in Minsk, Belarus, but that both sides had agreed to carry out a prisoner exchange Friday.

"The Minsk talks continue, but it is early to talk about any agreements," Zakharchenko was quoted as saying by Russia's Tass news agency. "The only thing I can say that we succeeded in reaching agreement on was the exchange of prisoners on the 'all-for-all' basis - 150 for 225."

But sources on both sides said there were last-minute glitches that held up the exchange. A Tass report suggested the delay was caused by a disagreement over the location where the two sides would release their captives.

Ukraine's Ukrinform news agency quoted a Defense Ministry adviser, Vasyl Budyk, as saying that "if all goes well, the exchange will begin tomorrow."

Then Russia's RIA Novosti reported late Friday that the exchange had begun at a site about 20 miles north of Donetsk, without providing further detail. Tass had said in the earlier report that the location of the swap was "being solved," suggesting that was at least one reason behind the delay.

Fighting in eastern Ukraine between government forces, volunteer battalions, and pro-Russia separatists has claimed more than 4,700 lives since spring.

Talks in September produced a cease-fire and an agreement to pull back heavy weapons, but the sides have failed to agree on a line of division and fighting continued.

Hostilities have diminished in recent weeks amid renewed peace efforts, but mutual suspicions and distrust have stymied progress.

Ukraine's parliament vote during the week to abandon the country's nonaligned status also has hampered talks. The renunciation of nonalignment is a first step toward Ukraine's eventual application to join NATO, a move staunchly opposed by Russia.