Ukrainian President Volodymyr Zelensky speaks to the media. File photo

President Volodymyr Zelensky vowed to wreak "wrath" against Russian forces in 2024, hours before Ukraine saw attacks on the first day of the year.

Russia and Ukraine have seen an escalation in strikes in recent days, including an unprecedented assault on the Russian city of Belgorod that killed 24 people on Saturday.

The attack came a day after Moscow launched a barrage of missiles and drones at Ukrainian cities, killing 39 people in one of the biggest aerial attacks since the war began.

January 1 is a day of mourning in Ukraine's capital Kyiv, where 19 people had been killed, city officials said.

Just hours after midnight on New Year's Day, the Russian-installed head of the occupied Donetsk region said four people had been killed and 13 wounded in "massive shelling" from rockets on its main city.

Flowers and toys are seen at a makeshift memorial to the victims in Belgorod, Russia, on Sunday. Reuters

In Ukraine's southern Odesa region, governor Oleg Kiper said one person died in a Russian drone attack, and three others were wounded.

And in western Ukraine's Lviv region, air defence systems shot down Russian drones in Monday's early hours, according to governor Maksym Kozytskyi.

Zelensky's televised New Year's address featured clips of Ukrainian artillery and fighter jets.

"Next year, the enemy will feel the wrath of domestic production," Zelensky said.

Agence France-Presse