Seoul "will not stand by but respond firmly in collaboration with the international community," South Korea said.

U KRAINE’S PRESIDENT, Volodymyr Zelensky, declared last week that North Korea is sending troops to Russia, in effect joining the invasion as a co-combatant. The appearance of one of the world’s most erratic and heavily-armed nations in the fight might test the best resourced and well-rested defences.

The Kremlin's alliance with North Korea may have bolstered its campaign in Ukraine, but it's come at a potentially serious cost. South Korea's government this week signaled its fury over the growing alliance between the two countries.