A large number of Russian casualties – between 63 to 400 according to different sources – were reported in a Ukrainian strike on a complex in the Moscow-occupied city of Makiivka on Monday.

The Russian Defense Ministry announced that 63 of its troops were killed in Makiivka, while Ukrainian sources claimed the number was as high as 400.

"As a result of a strike by four missiles with a high-explosive warhead on a temporary deployment point, 63 Russian servicemen were killed," the Defense Ministry said in a statement.

Ukraine's military, on the other hand, said nearly 400 Russian troops were killed in Makiivka in the Moscow-controlled part of the eastern region of Donetsk. It did so however without claiming the strike.

Kyiv said earlier Monday it had shot down all Russian drones in a massive wave of attacks, after Moscow launched an unprecedented third straight night of air strikes against civilian targets, intensifying its air war for the New Year holiday.

Russia has seen in the new year with nightly attacks on Ukrainian cities, including Kyiv, hundreds of kilometers from the front lines. That marks a change in tactics after months in which Moscow usually spaced such strikes around a week apart.

After firing dozens of missiles on Dec. 31, Russia launched dozens of Iranian-made Shahed drones on Jan. 1 and Jan. 2. But Kyiv said on Monday it had shot down all 39 drones in the latest wave, including 22 shot down over the capital.

Kyiv said the new tactic was a sign of Russia's desperation as Ukraine's ability to defend its air space had improved.

Russia had been trying to destroy Ukraine's energy infrastructure for months but had failed as Ukraine obtained better defenses, presidential chief of staff Andriy Yermak said on Telegram.

"Now they are looking for routes and attempts to hit us somehow, but their terror tactics will not work. Our sky will turn into a shield."

President Volodymyr Zelenskyy praised Ukrainians for showing gratitude to the troops and one another and said Russia's efforts would prove useless.

"Drones, missiles, everything else will not help them," he said of the Russians. "Because we stand united. They are united only by fear."

Ukraine's air defense systems worked through the night to bring down incoming drones and to warn communities of the approaching danger.

"It is loud in the region and in the capital: night drone attacks," Kyiv Governor Oleksiy Kuleba said.

"Russians launched several waves of Shahed drones. Targeting critical infrastructure facilities. Air defense is at work."

Russia, which has seized and claims to have annexed around a fifth of Ukraine, has turned to mass air strikes against Ukrainian cities since suffering humiliating defeats on the battlefield in the second half of 2022.

It says its attacks, which have knocked out heat and power to millions in winter, aim to reduce Kyiv's ability to fight. Ukraine says the attacks have no military purpose and are intended to hurt civilians, a war crime.

'Massive blow'

Russian nationalist war bloggers seethed with anger Monday after reports of mass casualties of soldiers housed alongside ammunition at a former vocational college in Makiivka, the twin city of a regional capital Donetsk in Russian-occupied east Ukraine. Unverified footage posted online showed a huge building reduced to smoking rubble.

A source close to the Russian-installed Donetsk leadership told Reuters dozens had died, although he called reports that the death toll was more than 100 exaggerated.

Daniil Bezsonov, a senior Russian-installed official in the Moscow-controlled parts of the Donetsk region, said the building had suffered a "massive blow" from U.S.-made rockets on New Year's Eve just after midnight. According to preliminary reports, it was being used as personnel quarters, he said.

"There were dead and wounded, the exact number is still unknown," Bezsonov said on the Telegram messaging app. "The building itself was badly damaged."

Russia's TASS state news agency said at least 63 people were injured. Ukraine's defense ministry said as many as 400 Russians were killed there "as a result of 'careless handling of heating devices.'"

Igor Girkin, a former commander of pro-Russian troops in east Ukraine who has emerged as one of the highest profile Russian nationalist military bloggers, said the death toll was in the hundreds, later editing his post to include wounded in that figure. Another nationalist blogger, Rybar, said around 70 were confirmed dead and more than 100 wounded.

"What happened in Makiivka is horrible," wrote Archangel Spetznaz Z, another Russian military blogger with more than 700,000 followers on Telegram.

"Who came up with the idea to place personnel in large numbers in one building, where even a fool understands that even if they hit with artillery, there will be many wounded or dead?"

New Year nightmare

Ukrainian troops saw the New Year on the front line in the eastern province of Donetsk.

One soldier, Pavlo Pryzhehodskiy, 27, played a song he had written on a guitar after 12 of his comrades were killed in a single night.

"It is sad that instead of meeting friends, celebrating and giving gifts to one another, people were forced to seek shelter, some were killed" during the New Year holiday, he told Reuters.

"It is a huge tragedy that cannot ever be forgiven."

In a nearby trench, soldier Oleh Zahrodskiy, 49, said he had volunteered after his son was called up as a reservist. Now, his son is in hospital, fighting for his life with a brain injury, while his father mans the front.

"It is very tough now," he said, holding back tears.

Russia has flattened Ukrainian cities and killed thousands of civilians since Putin ordered his invasion in February, saying Ukraine was an artificial state whose pro-Western outlook threatened Russia's security.

Ukraine has fought back with Western military support, driving Russian forces from more than half the territory they seized. In recent weeks, the front lines have been largely static, with thousands of soldiers dying in intense warfare.

In a stern New Year's Eve message filmed in front of a group of people dressed in military uniform, Putin vowed no let-up in his war.

"The main thing is the fate of Russia," Putin said. "Defense of the fatherland is our sacred duty to our ancestors and descendants. Moral, historical righteousness is on our side."