ZHOLOBOK, Ukraine (AP) — Ukrainian military and separatist representatives exchanged dozens of prisoners under cover of darkness at a remote frontline location Saturday evening, kicking off a process intended to usher in peace to the conflict-ridden east.

There were 139 Ukrainian troops and 52 rebels exchanged, according to a separatist official overseeing the prisoner swap at a no man’s land location near the village of Zholobok, some 12 miles west of the rebel-held city Luhansk.  

A busload of Ukrainian soldiers in military fatigues was transported earlier in the day from the main rebel stronghold of Donetsk to a rural spot some 90 miles to the northeast, before joining up with other groups of fellow captives.

After arriving at the location near Zholobok, the troops were made to line up and listen to a speech by a rebel representative, who ordered the men to leave the territory claimed by the separatist movements in the regions of Donetsk and Luhansk.

The soldiers — some of them using crutches, while one was carried on a stretcher — then walked for around 2 miles to a rendezvous point.

Ukrainian President Petro Poroshenko wrote on his Twitter account that he was informed the process had begun by the national security service. His spokesman, Svyatoslav Tsegolko, later said one more Ukrainian soldier prisoner was to be freed in the coming days.

The peace agreement signed last week in Minsk foresees an exchange of all prisoners in the conflict. It is unclear how many are held in total on both sides, although the Donetsk separatists have said Ukraine is holding about 580 rebels as prisoners.

Rebels said the bulk of the Ukrainian soldiers being released Saturday were captured during recent fighting for the strategic town of Debaltseve, which was taken over by separatists in the past week.

The self-styled Donetsk People’s Republic added in a statement that most of the people handed over by Ukrainian authorities were civilians.

But “fewer than 50 percent of those exchanged (by the Donetsk People’s Republic) were military prisoners,” the statement said.

The rebel statement cited what it said were observers at the swap saying many of the prisoners released by the Ukrainian government showed signs of maltreatment.

“Some prisoners could not make their own way independently. Meanwhile, all of the military prisoners transferred to the Ukrainian representatives were in good shape,” it said.

An Associated Press journalist saw at least one person released by government forces being pushed in a wheelchair.

Ukrainian authorities didn’t immediately respond to the rebels’ claims. They have earlier complained bitterly that their troops have been severely mistreated by their rebel captors. Ukrainian soldiers taken prisoner after the separatists seized the airport in Donetsk from government forces in January were forced to parade through the city and subjected to physical and verbal abuse by fighters and residents.