US officials have claimed that North Korea is suffering mass casualties on the front lines of Russia’s war against Ukraine, as Biden pushes to send a £1bn boost to Kyiv.White House spokesperson John Kirby told reporters on Friday that thousands of North Korean troops had been killed or wounded in the last week alone.

Russia is deploying “human waves” of North Korean soldiers, the U.S. said, and one soldier captured by Ukraine died of his injuries. Others died by suicide.