The U.S. on Friday designated Russia’s Wagner group as a “transnational criminal organisation,” piling pressure on the private Russian army fighting in Ukraine. White House national security spokesman John Kirby said Wagner, controlled by Yevgeny Prigozhin, a businessman close to President Vladimir Putin, has about 50,000 fighters in Ukraine, 80% of them drawn from prisons.

Mr. Kirby showed U.S. intelligence photographs of North Korea supplying arms to Wagner for its Ukraine operations, and said the private army has become a rival to the formal Russian military.

The photographs, from November 18-19, show Russian rail cars entering North Korea, picking up a load of infantry rockets and missiles, and returning to Russia, he said.

He said the U.S. Treasury was designating Wagner as a transnational criminal organisation, putting it in league with Italian mafia groups and Japanese and Russian organised crime.

The designation will allow the wider application of sanctions on the group’s sprawling global network, which includes mercenary operations as well as businesses in Africa and elsewhere.