Ukraine's military chief said on Sunday his country's forces were facing a difficult situation in fighting in the Kharkiv region, but that they were doing all they could to hold the line.

Russia launched a new assault from its territory into the northern Ukrainian region of Kharkiv on Friday, threatening to open a new front in the 27-month war. Moscow said on Saturday it had captured five villages, while Kyiv said it was repulsing the attacks and battling for control of the settlements.

"Units of the Defense Forces are fighting fierce defensive battles, the attempts of the Russian invaders to break through our defenses have been stopped," Syrskyi wrote on the Telegram app.