Ukrainian authorities and Russia-backed separatists in the war-torn east of the country began a prisoner exchange yesterday in a frontline operation that has stirred controversy.

The exchange came after Russian President Vladimir Putin and Ukrainian leader Volodymyr Zelensky held their first face-to-face talks in Paris on December 9 and agreed measures to de-escalate Europe’s only active war.

As part of the swap, Kiev was expected to hand over to separatists several riot policemen suspected of killing protesters during a pro-Western uprising in 2014, in a move that sparked public anger. “At the Mayorske checkpoint the process of releasing detained persons has begun,” the official Twitter account of the Ukrainian presidency said.

It was still unclear how many people were involved in the exchange. A Ukrainian source told AFP that the parties were still verifying the lists of those being exchanged.

A representative of the separatist stronghold of Donetsk, Daria Morozova, said earlier that separatists would get 87 prisoners, while 55 people would be handed over to Kiev.

Earlier Sunday the two sides were seen preparing to exchange prisoners, with vehicles arriving near the village of Odradivka, some 10 kilometres (6 miles) from the self-proclaimed Donetsk People’s Republic, an AFP correspondent reported from the scene.

The location was guarded by uniformed men with machine guns. The December summit between the Russian and Ukraine leaders, mediated by France and Germany, was the first of its kind in three years. The latest swap comes three months after Ukraine carried out a long-awaited exchange with Russia of 35 prisoners each.