North Korean troops fighting for Russia have been pulled from the front line for extra training after crude tactics led to massive casualties.

North Korea entered the war in November when Kim Jong-un sent an estimated 11,000 troops to help Russia push Ukrainian troops out of the Kursk region, sparking fears of a major escalation.

But Ukrainian special forces units fighting in Kursk say they have not seen any North Koreans for around three weeks.

American officials separately told the New York Times that North Koreans had not been seen at the front for a fortnight, attributing the withdrawal to heavy casualties.

The officials said the troops may return after receiving reinforcements and additional training.

Ukrainians who have fought the North Koreans have described them as committed fighters who often choose suicide over surrender, but who are hampered by unfamiliar terrain, outdated equipment and poor tactics.

A diary recovered from the body of a North Korean soldier in December revealed that infantry had been ordered to act as live “drone bait” so that Ukrainian unmanned aerial vehicles (UAVs) could be shot down.