Russian forces attacked energy infrastructure in Ukraine's northeastern Sumy region overnight, local authorities have said.
Air defences are said to have shot down 16 drones.
Power was cut in some districts and back-up systems had to be used, authorities said.
Damage was caused in the areas of Konotop, Okhtyrka and Sumy city, officials said on Telegram.
Water facilities had to switch to emergency power.
Acting mayor Artem Kobzar said there were no casualties in the city and energy workers were conducting repairs.
The targeting of critical infrastructure has been a signature Russian strategy in recent months.
The UK government has noted that power plants, electricity substations and gas storage facilities have all been attacked.
