“It has been identified that equipment and anti-aircraft missiles aimed at reinforcing Pyongyang’s vulnerable air defence system have been delivered to North Korea,” Shin Won-sik, Seoul’s top security advisor, told local broadcaster SBS.

Russia also appears to have provided Kim Jong-un with financial and technological support for its space programme following a failed spy satellite launch earlier this year, Mr Shin added, a claim corroborated by Western intelligence.

Analysts fear that Russia may decide to transfer sophisticated weapons technology to enhance North Korea’s nuclear-capable missiles, although they say Moscow is unlikely to do this in the initial stage of Pyongyang’s troop deployment.

Earlier this week, Seoul said Pyongyang had transferred more than 13,000 containers of artillery, missiles and other conventional arms to Russia since August 2023 to replenish its diminishing stock piles.