A large-scale prisoner exchange between Russia and Ukraine -- the only concrete outcome of peace talks -- was thrown into doubt Saturday after Moscow and Kyiv accused each other of delaying and thwarting the swap.

Russia and Ukraine held a second round of peace talks where they agreed to exchange more prisoners and to return the bodies of 12,000 dead soldiers.

A planned exchange of Russian and Ukrainian prisoners of war failed to take place on Saturday, with Moscow accusing Kyiv of postponing the swap at the last minute, which Ukrainian officials dismissed as more “dirty games” from the Kremlin.