According to the US government, tens of thousands of mercenaries from the Russian “Wagner” combat group are stationed in Ukraine.

It is estimated that 50,000 mercenaries are currently deployed in Ukraine, including 40,000 convicts, White House communications director John Kirby said in Washington on Thursday.

In the past few weeks alone, around 1,000 "Wagner" fighters have been killed in battles.

Around 90 percent of them were convicts, Kirby said.

The prisoners came from Russian prisons.

In certain cases, the Russian military is under the command of the "Wagner" group.

Kirby also stated that "North Korea has completed an initial arms shipment to 'Wagner'" - the mercenary group paid for it.

"We assume that the amount of material supplied to 'Wagner' will not change the dynamics on the battlefield and in Ukraine, but we are certainly concerned that North Korea is planning to supply more military equipment ."

"It's despicable"

US Ambassador to the UN Linda Thomas-Greenfield said North Korea had delivered the weapons last month.

"It is despicable that Russia, a permanent member of the UN Security Council - in violation of UN Security Council resolutions - is now using weapons from North Korea and Iran to conduct its war of aggression against Ukraine," Thomas-Greenfield said.

Russian businessman Yevgeny Prigozhin, known for his close ties to Kremlin boss Vladimir Putin, publicly admitted for the first time in September that he had founded the notorious mercenary group.

Prigozhin explained that he formed the unit in 2014 for use on the Russian side in the Ukrainian Donbass.

He also confirmed operations of the "Wagner" group in Syria, other Arab countries as well as in Africa and Latin America.

"Wagner" mercenaries were also in Sudan, Mali and Libya.

Putin has always denied that the mercenary group was formed at the behest of the Kremlin and used to support the Russian army.

Prigozhin "literally puts people through a meat grinder" in Ukraine, Kirby said.

He doesn't care about human life, especially Ukrainian ones.

"But I would go so far as to say not in Russian either," Kirby said.

He announced that the government would impose new sanctions on the mercenary force.