Russia said Sunday that trains carrying more bodies of Ukrainian soldiers were due to depart towards the Ukrainian border, escalating a spat with Kyiv over a prisoner of war swap.

Ukraine has unexpectedly postponed exchanging prisoners of war and accepting the bodies of killed soldiers for an indefinite period, Kremlin aide Vladimir Medinsky said on Saturday.Russia and Ukraine held the second round of peace talks in Istanbul on Monday where they agreed to exchange more prisoners - focusing on the youngest and most severely wounded - and to return the bodies of 12,

Russia claims Ukraine indefinitely postponed the release while Kyiv maintains it has been delayed until next week.

The large-scale attack comes days after Trump says Putin had "very strongly" promised response to Ukraine "Spider web" attack.

U.S. President Donald Trump says he's spoke with Russian President Vladimir Putin and that the Russian leader told him “very strongly” that he will respond to Ukraine’s weekend drone attack on Russian airfields.