Both Russia and Ukraine have reported overnight attacks, with Ukraine's energy infrastructure damaged.
The Ukrainian energy ministry said three workers at an energy facility were injured and some residents lost power.
A thermal power plant was seriously damaged in a Russian attack, energy firm DTEK said, although it didn't name the plant.
Meanwhile, attacks were reported in the Russian regions of Tambov and Adygeya.
A fire broke out after an explosion at the Platonovskaya fuel depot in the Tambov region in central Russia, likely due to a drone attack, regional governor Maksim Yegorov said on Telegram.
No one was hurt in the incident, he said, and firefighters were working at the site.
Another fire broke out at a fuel depot in the Adygeya region in the North Caucasus following a Ukrainian drone attack, regional head Murat Kumpilov said.
The TASS news agency, citing Russia's defence ministry, said air defences had downed 15 Ukrainian drones overnight - including six over Adygeya.
