Ukraine says around 400 Russian soldiers have died in a missile attack on the occupied Donetsk region.
Russian officials have contested the figure, admitting to only 63 of their troops being killed in the blast. Neither claim has been verified.
The attack hit a building in the city of Makiivka, where Russian forces were thought to be stationed.
Meanwhile in Kyiv, air raids sounded on Sunday night, as the latest wave of strikes from Russia continued.
In a statement on Monday, Russia's defence ministry said Ukrainian forces fired six rockets using the US-made Himars rocket system at a building housing Russian troops. Two of them were shot down, it added.
Daniil Bezsonov, a senior Russian-backed official in the occupied parts of Donetsk, earlier said the missile struck Makiivka two minutes after midnight on New Year's Day.
"A massive blow was dealt to the vocational school," he said. "There were dead and wounded."
Although access to Russian-controlled areas is restricted, a number of Russian commentators and bloggers acknowledged the attack - but suggested the numbers were lower than claimed.
Vladimir Solovyov, a Russian presenter, shared a Telegram saying "losses were significant... but not even close" to 400.
But Igor Girkin, a pro-Russian commentator, said hundreds had been killed and wounded, although the exact number was still unknown because of the large number still missing. The building itself was "almost completely destroyed", he said.
He added that the victims were mainly mobilised troops - that is, recent conscripts, rather than those who chose to fight. He also said ammunition was stored in the same building as the soldiers, making the damage worse.
"Almost all of the military equipment was also destroyed, which stood right next to the building without any disguise whatsoever," he wrote on Telegram.
Girkin is a well-known military blogger, who led Russian-backed separatists when they occupied of large parts of eastern Ukraine in 2014. He was recently found guilty of murder for his part in the shooting down of flight MH17.
Despite his pro-Russian stance, he regularly criticises the Russian military leadership and their tactics.
According to the Ukrainian military, 300 were wounded in addition to the estimated 400 killed.
Ukraine's army claims, almost daily, to have killed dozens, sometimes hundreds, of soldiers in attacks, so caution is needed. But if the claims are confirmed, this could be one of the deadliest attacks by Ukraine on Russian targets in the war.
Ukraine has not confirmed the strikes were carried out with Himars missiles, maintaining a long-held strategy of not releasing details about its attacks.
It merely said, sarcastically, that the deaths were the result of "careless handling of heating devices, neglect of safety measures, smoking in an unidentified place".
The Russian-installed administration said at least 25 rockets were fired at the region overnight on New Year's Eve.
https://www.bbc.com/news/world-europe-64142650
