Russia accuses Ukraine of postponing prisoner exchange

Ukraine has unexpectedly postponed exchanging prisoners of war and accepting the bodies of killed soldiers for an indefinite period, Kremlin aide Vladimir Medinsky says.

Russia and Ukraine held the second round of peace talks in Istanbul on Monday, agreeing to exchange more prisoners - focusing on the youngest and most severely wounded - and return the bodies of 12,000 dead soldiers.

"In strict accordance with the Istanbul agreements, on June 6, Russia began a humanitarian operation to hand over to Ukraine more than 6000 bodies of killed Ukrainian servicemen, as well as to exchange wounded and seriously ill prisoners of war and prisoners of war under the age of 25," Medinsky said on Telegram.

He said 1212 bodies of killed Ukrainian soldiers were in refrigerated containers at the exchange point.

Russia has also handed over to Ukraine the first list of 640 prisoners of war, categorised as "wounded, seriously ill and young people", to begin the exchange, Medinsky said.

"The Russian Defence Ministry's contact group is on the border with Ukraine," he said, adding that Ukrainian negotiators were not at the exchange location.

Ukrainian officials responsible for the exchanges did not respond to a request for comment.

Medinsky urged Ukraine to strictly adhere to the schedule and the agreements and to immediately proceed with the exchange.

"We are on site. We are fully prepared to work," he said.

"International TV channels, news agencies and correspondents are welcome to come and see for themselves that this is indeed the case."