North Korea has sent additional troops to Russia, after mass casualties in the previous deployment that fought in Ukraine, a new assessment has found.

The exact number of additional troops deployed by North Korea will be determined by South Korea’s national intelligence service (NIS), but local reports estimate the increase at between 1,000 and 3,000 soldiers.

The troops were redeployed to Russia’s Kursk region in early February following a temporary withdrawal.

Volodymyr Zelensky, the Ukrainian president, said earlier this month that North Korean troops were back on the front lines, which was confirmed by the South Korean intelligence agency on Thursday.

NIS said: “Following a month-long lull, North Korean troops were placed back in the frontline region of Kursk starting in the first week of February.”

North Korea sent around 10,000-12,000 troops to Russia last year and has supplied vast amounts of conventional weapons.

In January, the NIS reported that about 300 North Korean soldiers were killed and 2,700 injured.

Mr Zelensky put the number of casualties at 4,000, while US estimates were around 1,200.

‘Drone bait’

Reports from Ukrainian soldiers who have encountered North Korean troops describe them as determined fighters who often refuse to surrender, frequently choosing death over capture.

However, their effectiveness is limited by unfamiliarity with the region, outdated equipment, and inadequate tactics.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 could be shot down.

Ukraine took the first two North Korean prisoners of war after repelling an assault last month.