The grainy mobile phone footage shows olive green-clad soldiers lining up for kit in a gloomy-looking military barracks.

The clips, which emerged late last week, are said to show the arrival of North Korean troops at a base in Russia, ahead of their expected deployment to join Vladimir Putin’s war against Ukraine.

Some 3,000 North Korean soldiers are already reported to be training in Russia and more than 10,000 are expected to be deployed in the coming weeks.

US officials briefed last week the deployment was “a very, very serious issue” and could involve concessions to Pyongyang from the Kremlin that would harm global security.

While Western officials said it is still not clear if the North Koreans are going into battle, Kyiv said at least the first tranche are on their way to fight Ukraine in Kursk.