A large power plant near Kiev was completely destroyed by Russian attacks early Thursday, energy company Centrenergo said.
Officials said the Trypillya power plant is the largest supplier of electricity to three regions, including Kyiv.
“The extent of the destruction is shocking,” said Centrenergo chairman Andriy Hota.
Russia has long targeted Ukraine’s energy system in a targeted and systematic manner.
Mr Hota told the BBC that Thursday morning’s strikes “destroyed the transformer, the turbines, the generators. They destroyed 100%”.
After Thursday’s large-scale airstrike, a fire broke out in the turbine workshop at the Trypillya plant, 50 km (31 miles) south of Kiev.
The Centrenergo boss said the facility was attacked by several rockets. The shift workers were able to escape because they ran for cover immediately after the first drone hit, he said.
Residents were asked to close their windows, charge all their devices and stock up on water.
More than 80 missiles and drones targeted locations across Ukraine in the early hours of Thursday. Many attacks targeted energy infrastructure and almost a third made it through Ukraine’s air defenses.
Hours later, Centrenergo confirmed that the Trypillya plant had been shut down. Mr Hota said his company’s entire generation capacity in Ukraine was now destroyed.
It was one of Ukraine’s largest suppliers of electricity and heat. It operated two other power plants – one in the Kharkiv region that was destroyed in late March and one in an area of the Donetsk region that was taken over by Russia in 2022.
According to Mr. Hota, the Kharkiv and Trypillya power plants used to generate about 8% of the country’s electricity. The Trypillya thermal power plant supplied electricity to the three central regions of Zhytomyr, Cherkasy and Kiev.
He believed that the destruction of the Trypillya plant would not be a critical issue for Ukraine in the summer, but that it would become a “huge problem” in the winter.
Although the plant could be rebuilt with the help of spare parts from Europe, it would be vulnerable to attacks even if Ukraine’s allies did not have strong air defenses.
“We can repair. We can do the impossible. But we need protection.”
At least two more thermal power plants suffered “significant damage” overnight in western Ukraine, putting even greater strain on the country’s electricity supply.
After repeated attacks in March, the capacity of the energy supplier DTEK had already fallen to 20%.
The company told the BBC that the recent missile and drone attack on these “purely civilian power stations” would complicate the task of supplying the grid with critical power.
“Attack after attack, Russia is trying to strangle Ukraine’s energy system and with it our hard-won freedom,” DTEK said.
The Kharkiv region in the northeast was hit hard again after its power plants suffered severe damage in late March.
The mayor there described the situation as “very difficult” and announced further power outages for households and companies.
On Thursday, the subway in Kharkiv temporarily suspended operations to save electricity. Operations have now resumed, but the power supply keeps breaking down, so the trains are only in operation very intermittently.
President Vladimir Putin said Thursday that Russia was “obliged to respond to the attacks on Ukrainian energy sites following Kiev’s attacks on Russian targets,” even though it was a war he started two years ago for no reason.
“Unfortunately, we have recently observed a number of strikes at our energy sites and have had to respond,” he said.
“I would like to emphasize that we did not carry out any attacks in the winter for humanitarian reasons either. What I mean by this is that we didn’t want to leave social institutions – hospitals and the like – without power. But after a series of attacks, we had to respond to our energy systems.”
“Energy attacks,” he added, are part of Russia’s goal of “demilitarizing” Ukraine – one of its stated goals when the invasion began in February 2022.
In another situation, a rare series of daily strikes left four people dead and several others injured in the southern city of Mykolaiv on Thursday.
Ukraine’s Southern Military Command said on Telegram that private homes, cars and industrial facilities were damaged in the “treacherous” attack.