Authorities in Russia say 18 people have been killed in a Ukrainian strike on a western provincial capital city.

Russia's ministry of emergency situations said on Saturday the attack on Belgorod near the border with Ukraine left 111 people injured.

It says the shelling hit the central part of the city. Footage taken at the site shows burning cars and broken windows of a building.

A spokesperson for the Russian defense ministry said that this crime will not remain unpunished.

Ukrainian authorities have not commented whether their military were involved in the attack.

Meanwhile, the death toll from a largest-scale Russian air strike on Ukraine rose as rescuers continued their search through rubble for the missing.

President Volodymyr Zelenskyy said on social media that, in total, 39 people have been killed and 159 injured.

In the capital Kyiv, authorities say they have so far confirmed 16 deaths.

Kyiv Mayor Vitali Klitschko said he declared January 1st a day of mourning in the city.