Russian forces launched missiles at energy infrastructure in Ukraine's northeastern Sumy region Tuesday, after carrying out a drone strike overnight, cutting power in some districts and forcing authorities to resort to back-up power systems.

"The enemy did not achieve its goal of destroying the energy system, but we now feel that it carries on with the intentions to destroy (the system) because it is now attacking with missiles and not with Shaheds," Sumy regional governor Volodymyr Artiukh said on national television.

According to preliminary estimates, Russian forces used at least four missiles in the latest attack, he said.

The Ukrainian air force said Russia launched 51 drones to attack the country on Tuesday and that its air defenses had shot down 34 of them in five regions.

The overnight attack did damage in the Konotop, Okhtyrka and Sumy districts and the critical infrastructure facilities were using back-up power systems, regional officials said via the Telegram messaging app. Sumy's acting mayor Artem Kobzar said there were no casualties in the city. Ukraine's energy ministry said the attack caused a fire at a power substation and cut power to more than 281,000 consumers. The power had since been partially restored, it said.

Artiukh could not say how the latest attack had affected work to restore the power.

Sumy regional authorities said air defenses had shot down 16 drones over the region overnight.