Uncertainty meanwhile remains whether Kyiv diplomats will attend a new round of peace talks proposed by Moscow for early next week in Istanbul.

Kyiv said it was committed to the search for peace, but that it was waiting for a memorandum from the Russian side setting out their proposals.

Ukraine attacked a Russian military object in the far-eastern city of Vladivostok on Friday, marking an escalation between the two countries ahead of an expected second round of talks next week.