Three thermal power plants of Ukraine's largest private power firm DTEK were attacked by Russia overnight, according to the company.
DTEK said some of their equipment was "severely damaged" in the attack.
"After the attack ended, the power engineers promptly started to repair the damage," the company said on the Telegram messaging app.
Ukrainian power grid operator Ukrenergo also said that both thermal and hydropower plants had been damaged in missile and drone attacks.
"During the night, the Russians struck again at energy facilities in a massive and combined attack," Ukrenergo said on the Telegram messaging app.
"Thermal and hydroelectric power plants in the central and western regions were damaged," it said.
Ukrenergo noted that emergency shutdowns were applied in the country's southeastern Dnipropetrovsk region.
