Kremlin spokesman Dmitry Peskov (Photo: REUTERS)

Kremlin aide Vladimir Medinsky, who heads the Russian delegation, is in contact with his Ukrainian counterpart, Peskov said.

Resuming negotiations after a gap of more than three years, the two sides held face-to-face talks in Istanbul on May 16 and June 2 that led to a series of prisoner exchanges and the return of the bodies of dead soldiers. But they have made no progress towards a ceasefire which Ukraine has been pressing for.

The conflict has intensified in recent weeks, with Russia carrying out some of its heaviest air attacks and Ukraine mounting surprise drone strikes on airfields.