Ukraine's air force on Wednesday said it shot down 39 of 55 missiles and 20 of 21 drones used for the attack, which piles more pressure on the energy system more than two years after Russia launched its full-scale invasion.
"Another massive attack on our energy industry!" Energy Minister German Galushchenko wrote on the Telegram app.
Two people were injured in the Kyiv region and one was hurt in the Kirovohrad region, Interior Minister Ihor Klymenko said.
Galushchenko said power generation and transmission facilities in the Poltava, Kirovohrad, Zaporizhzhia, Lviv, Ivano-Frankivsk and Vinnytsia regions were targeted.
Some 350 rescuers raced to minimise the damage to energy facilities, 30 homes, public transport vehicles, cars, and a fire station, the interior ministry said.
National power grid operator Ukrenergo said it was forced to introduce electricity cuts in nine regions for consumers and that it would expand them nationwide for businesses during peak evening hours until 11pm.
Ukrenergo CEO Volodymyr Kudrytskyi, interviewed by the Ukrainska Pravda media outlet, said electricity imports would not make up for power shortages. He said hydropower stations had also been hit, clarifying an earlier company statement omitting hydro stations from the list of affected facilities.
Power cuts for industrial users, he said, were "almost guaranteed" but interruptions for domestic users would depend on how well they reduced consumption.
"Many important power stations were damaged," he said, citing three stations operated by DTEK, Ukraine's biggest private company, as well as two hydropower stations.
"The damage is on quite a large scale. There is a significant loss of generating power, so significant that even imports of power from Europe will not cover the shortage that has been created in the energy system."
Russia's defence ministry said it struck Ukraine's military-industrial complex and energy facilities in retaliation for Kyiv's strikes on Russian energy facilities.
"As a result of the strike, Ukraine's capabilities for the output of military products, as well as the transfer of Western weapons and military equipment to the line of contact, have been significantly reduced," the ministry said.
Russian strikes again targeted Ukrainian infrastructure more than two years since the war began. (AP PHOTO)
President Volodymyr Zelenskiy noted the attacks were launched on the day Ukraine marks the end of World War II.
"This is how the Kremlin marks the end of World War Two in Europe, with a massive strike, attempting to disrupt the lives of our people with its Nazism," he said in his nightly video address.
In an earlier online address, Zelenskiy singled out what he said was the West's limited progress in curbing Russian energy revenue and some countries that attended President Vladimir Putin's inauguration for a fifth term in the Kremlin on Tuesday.
Fighting Nazism back then, he said, was "when humanity unites, opposes Hitler, instead of buying his oil and coming to his inauguration".
Ukraine has stepped up drone attacks on Russian refineries this year despite apparent objections by the United States, trying to find a pressure point against the Kremlin whose forces are slowly advancing in the eastern Donbas region.
Ukrainian strikes on Russian refineries may have disrupted more than 15 per cent of Russian oil refining capacity, a NATO military alliance official has said.
After pounding the energy system in the first winter of the war, Russia renewed its assault on the grid in March as Ukraine was running low on stocks of Western air defence missiles.
Prime Minister Denys Shmyhal estimated that more than 800 heating facilities had been damaged and up to 8GW of power generation lost so far, adding the government needed $US1 billion to fund repair work.
