Ukrainian President Volodymyr Zelensky denounced Wednesday an "inhumane" attack from Russia, which launched over 170 missiles and drones, knocking out power in several regions on Christmas Day and killing an energy worker.
The country woke up at 5:30 am (0330 GMT) to an air raid alarm, followed shortly by air force reports that Russia had launched Kalibr cruise missiles from the Black Sea.
"Putin deliberately chose Christmas to attack. What could be more inhumane? More than 70 missiles, including ballistic missiles, and more than a hundred attack drones. The target is our energy system," Zelensky said, AFP reported.
This was the 13th large-scale strike on Ukraine's energy system this year, the latest in Russia's campaign targeting the power grid during winter.
"Russian evil will not break Ukraine and will not ruin Christmas," Zelensky said.
Russia meanwhile said five people had died in Ukrainian strikes and from a falling drone in the border region of Kursk and in North Ossetia in the Caucasus.
Ukraine said its air force downed 58 out of 79 Russian-launched missiles. It did not, however, down the two North Korean-made KN-23 ballistic missiles launched by Russia.
US President Joe Biden called "outrageous" the strikes that cut off people's access to heat and electricity amid winter conditions.
"I have directed the Department of Defense to continue its surge of weapons deliveries to Ukraine, and the United States will continue to work tirelessly to strengthen Ukraine's position in its defense against Russian forces," he added in a statement.
Ukraine has been urging allies to send more aid to fend off aerial strikes and push back troops on the ground.
Earlier, British Prime Minister Keir Starmer condemned the strikes.
"I pay tribute to the resilience of the Ukrainian people, and the leadership of President Zelensky, in the face of further drone and missile attacks from Putin's bloody and brutal war machine with no respite even at Christmas," Starmer said.
Kyiv also said a Russian missile went through Moldovan and Romanian airspace, but Romania said it detected no such violation.
Moldova, which has expressed solidarity with Ukraine since the war, "confirmed a violation" of its airspace later Wednesday.
While its military radar did not identify the missile, "Russia deliberately flew these devices at a very low altitude to avoid detection", a presidency spokesperson told AFP.
Ukraine's DTEK energy company said the attack severely damaged equipment at thermal power plants.
"Denying light and warmth to millions of peace-loving people as they celebrate Christmas is a depraved and evil act that must be answered," the company's CEO Maxim Timchenko said.
The employee of a Ukrainian thermal power plant was killed in the central Dnipropetrovsk region, over which 42 missiles were shot down, governor Sergiy Lysak said.
Heating was cut in several parts of the city of Dnipro, said its mayor Borys Filatov, who added authorities were evacuating and transferring patients from a hospital.
"Christmas morning has once again shown that nothing is sacred for the aggressor country," Svitlana Onyshchuk, the head of the Ivano-Frankivsk region, which also temporarily lost power.
Ukraine is officially celebrating Christmas on December 25 for the second time.
The government last year changed the date from January 7, when most Orthodox believers celebrate, as a snub to Russia.
Nearly 200 people paraded through the centre of Kyiv, singing Christmas carols.
"With this march, we show that we will not be discouraged," 30-year-old Bogdana Kuevda, one of the participants, told AFP.
The Christmas day attack also targeted Kharkiv, Ukraine's second largest city, located near the Russian border.
The missiles had targeted the city's boiler houses, thermal power plants and electricity facilities, mayor Igor Terekhov said, temporarily cutting power to 500,000 people.
Kharkiv's governor Oleg Synegubov also said authorities had evacuated 46 people from the area of Borivske and Kupiansk.
Moscow's forces are aiming to recapture the town of Kupiansk, which was occupied in the first year of the war but later retaken by Ukrainian forces.
Outnumbered Ukrainian troops are now on the back foot across the front line in the Kharkiv and Donetsk region further south, ceding ground to better-equipped Russian troops.
Russia said it seized the small village of Vidrodzhennia, a few kilometres south of Pokrovsk, a vital rail hub and mining town.
Both sides are scrambling to gain an upper hand ahead of the inauguration of US President-elect Donald Trump, who boasted he would quickly end the war, raising fears that Washington may force Kyiv into a deal on Moscow's terms.
