Russian strikes on Ukrainian power infrastructure have left millions with disrupted light, heating and water supplies, pushing the war-battered country towards humanitarian crisis.

Zelensky said in an evening address to the nation Wednesday that Russia was preparing even more large-scale drone and missile attacks on the country.

The Ukrainian Hydrometeorological Center said that between February 1 and 3, night temperatures could dip as low as minus 30C in parts of the country.

Kyiv city officials said on Thursday there were 613 buildings in the capital without heating following several aerial attacks.