Ukraine says it has killed around 400 Russian soldiers in a missile attack on the occupied Donetsk region.
The missile targeted a building in the city of Makiivka, where Russian forces were thought to be stationed.
The figure has not been verified. Pro-Russian authorities acknowledged casualties, but did not confirm the figures being reported.
In Kyiv, air raids sounded on Sunday night, as the latest wave of drone and missile strikes from Russia continued.
Daniil Bezsonov, a senior Russian-backed official in the occupied parts of Donetsk, said the missile struck Makiivka two minutes after midnight on New Year’s Day.
“A massive blow was dealt to the vocational school from American MLRS Himars,” he said, referring to US-provided missiles.
“There were dead and wounded, the exact number is still unknown,” Bezsonov added in a post on the messaging app Telegram.
A number of Russian commentators and bloggers acknowledged the attack – but suggested the numbers were lower than claimed.
Vladimir Solovyov, a Russian presenter, wrote on Telegram “losses were significant… but not even close” to 400.
According to the Ukrainian military, 300 people were wounded in addition to the estimated 400 killed.
The Russian-installed administration said at least 25 rockets were fired at the region overnight on New Year’s Eve.
Hours after the strike in Makiivka, Kyiv came under fire. A drone and missile attack targeted critical infrastructure, the Ukrainian capital’s regional governor Oleksiy Kuleba said.
One man in Kyiv was injured by debris from a destroyed Russian drone, the capital’s mayor added.
It came after Ukrainian president Volodymyr Zelensky wished for victory and a “return to normal” for Ukraine in 2023.
In a new year address on Russian TV, President Vladimir Putin said Russia would fight to protect its sovereignty and independence.
Kyiv’s military issued a warning of the latest attacks just after 01:00 (23:00 GMT) on Monday.
“Air attack on Kyiv… air alert is on in the capital,” it announced on Telegram.
Serhiy Popko, the city’s military administration head, told people to stay in shelters.
Mr Kuleba, the regional governor, said the weapons were Iranian-made Shahed drones, adding that they were “targeting critical infrastructure facilities”.
“The main thing now is to stay calm and stay in shelters until the alarm is off,” he said.
Russia has been targeting Ukraine’s energy infrastructure for several months, destroying power stations and plunging millions into darkness during the country’s freezing winter.