Over 20,000 Russian fighters killed since Dec 2022: US

More than 20,000 Russian soldiers were killed and over 100,000 were wounded since December 2022, White House official John Kirby said, according to CNN.

While talking to reporters, Kirby, on Monday, said that Russia has 'exhausted its military stockpiles and its armed forces' and since December, the United States estimates Russia has suffered more than 100,000 casualties, including over 20,000 killed in action.

Kirby, who serves as National Security Council coordinator for strategic communications, noted that nearly half of those casualties were fighters with the Russian private company Wagner.

Kirby lambasted a recent assertion from Wagner leader Yevgeny Prigozhin, who said Sunday that his group had only suffered 94 casualties.

Kirby called Prigozhin's comments 'just a ludicrous claim'.

Pressed on the source of the new 100,000 figure, Kirby said it was 'based on some downgraded intelligence that we've been able to collect'.

He declined to provide information on Ukrainian casualties, noting that the US has 'never' provided such information and would defer to Ukraine on the matter, reported CNN.

Kirby added that the Ukrainians 'are the victims here, Russia is the aggressor, and I'm simply not going to put information in the public domain that's going to, again, make it any harder for the Ukrainians'.

Meanwhile, the Ukrainian military said that it is locked in a 'positional struggle' as fierce fighting continues to rage in Bakhmut, adding it has been able to push back Russian forces after a series of counterattacks.

"I can definitely confirm the information that the enemy in Bakhmut left some positions after some of our counterattacks," Serhii Cherevatyi, the spokesperson for the Eastern Grouping of the Ukrainian Armed Forces, told a national broadcaster.

"There is a positional struggle there," Cherevatyi said, explaining that the frontline was constantly shifting.

"Sometimes the enemy has some success after a powerful artillery strike and the destruction of infrastructure, and they can move forward. But we counterattack and often win back our positions after inflicting fire on the enemy," Cherevatyi added.

Earlier, a Russian freight train derailed on Monday in the western region of Bryansk bordering Ukraine after an 'explosive device' detonated on the rail tracks, the local governor said, according to The Moscow Times.

"An unidentified explosive device went off, as a result of which a locomotive of a freight train derailed," Bryansk governor Alexander Bogomaz said on Telegram.

Bogomaz said the device went off 'on the 136th kilometre' of the railroad between regional hub Bryansk and the town of Unecha, towards the border with Ukraine.

"There were no casualties," he added.

Pictures shared on social media showed several of a train's tank carriages laying on their side and dark grey smoke billowing into the air at the site of the derailment, in the Bryansk region.

The attack came a day after a Ukrainian strike killed four people in a Russian village in the Bryansk region and as Kyiv prepared for a widely expected counter-offensive, reported The Moscow Times.

Meanwhile, Russia's defence ministry says its forces had carried out missile strikes against Ukrainian military targets overnight, state-owned Ria news agency reported.

The defence ministry said all its designated targets, including weapons depots and ammunition factories, had been hit.