The Russian defence ministry said it launched a strike on "critically important facilities of gas and energy infrastructure that ensure the functioning of Ukraine's military industrial complex".
It did not give the target locations or other details.
The barrage came a day after Moscow vowed a response to what it said was an attack on Russian soil using multiple Western-supplied missiles.
Kyiv has not confirmed that attack, though it said Tuesday it hit an oil refinery and a fuel storage depot, a chemical plant producing ammunition and two anti-aircraft missile systems, in a missile and drone attack that reached about 1100km into Russia.
Long-range attacks have been a feature of the nearly three-year war, where on the front line snaking about 1000km from northeast to southern Ukraine, the armies have been engaged in a war of attrition.
Russia has been advancing on the battlefield over the past year, though its progress has been slow and costly.
Russia attacked Ukraine with 43 missiles and 74 drones overnight, the Ukrainian air force said.
Another massive Russian attack. It's the middle of winter, and the target for the Russians remains unchanged: our energy infrastructure. Among their objectives were gas and energy facilities that sustain normal life for our people. Over 40 missiles were launched in this attack,…— Volodymyr Zelenskyy / Володимир Зеленський (@ZelenskyyUa) January 15, 2025
A total of 30 missiles and 47 drones were shot down, and 27 drones failed to reach their target, it said.
The Russian missiles sought out targets from the Lviv region in western Ukraine near Poland to Kharkiv in northeast Ukraine bordering Russia.
The state energy company Ukrenergo reported emergency power outages in six regions.
It often shuts down production during attacks as a precaution.
"The enemy continues to terrorize Ukrainians," Energy Minister Herman Halushchenko wrote on Facebook.
Russia has repeatedly tried to cripple Ukraine's power grid, denying the country heat, electricity and running water in an effort to break the Ukrainian spirit.
The attacks have also sought to disrupt Ukraine's defence manufacturing industry.
Ukrainian authorities try to rebuild their power generation after the attack, though the barrages have eroded production.
Western partners have been helping Ukraine rebuild.
"It is the middle of the winter, and Russia's goal remains unchanged: our energy infrastructure," Ukrainian President Volodymyr Zelenskiy said on Telegram.
He urged Western partners to accelerate the delivery to Ukraine of promised air defence weapons, emphasising that "promises have been made but not yet fully realised".
