The United States said on Monday it was Russia that is escalating the conflict in Ukraine by deploying North Korean troops, after the Kremlin warned that Washington would deepen its involvement in the war by allowing Kyiv's forces to strike far into Russia with U.

"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.