"The scale of deployed North Korean troops is being closely watched," Yoon Yeocheol, South Korea's ambassador to the U.K., told Newsweek.

Ukrainian and South Korean intelligence services have said that many of the troops deployed to Russia are some of Pyongyang’s best, drawn from the 11th Corps, also known as the Storm Corps - a unit trained in infiltration, infrastructure sabotage and assassinations.

North Korea may deploy as many as 100,000 troops to aid Russia’s war on Ukraine if the alliance between Pyongyang and Moscow continues to deepen, according to people familiar with assessments made by some Group of 20 nations.