MOSCOW, June 7 (Xinhua) -- Russia on Saturday accused Ukraine of indefinitely delaying a planned exchange of prisoners and the handover of fallen soldiers' bodies.

Russia has handed over the first list of 640 prisoners to Ukraine and begun transferring bodies of dead Ukrainian soldiers, but Ukrainian negotiators did not arrive at the exchange site, Russian Presidential Aide Vladimir Medinsky said in a telegram post.

He called on Ukraine to "strictly adhere to the schedule and all agreements reached, and to immediately begin the exchange."

Kiev did not immediately respond to the accusation.

During their last round of talks in Istanbul on Monday, the two sides agreed on an "all-for-all" exchange involving seriously ill and wounded prisoners, as well as soldiers under the age of 25, according to Medinsky.

Ukrainian President Volodymyr Zelensky said Wednesday that a prisoner exchange under a "500-for-500" formula would take place this weekend. ■