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.

"We can be certain [North Korea] will ask for a high price from Russia in return," the British ambassador to the United Nations claimed.

President Vladimir Putin welcomed his Chinese counterpart, Xi Jinping, to Russia on Tuesday, as the Kremlin head prepares to host several leaders of developing nations at an intergovernmental summit this week.

The BRICS summit in Russia will be the "the largest foreign policy event ever held" by Russia, Kremlin foreign affairs adviser Yuri Ushakov has said. The summit with include 36 countries with over 20 represented by heads of state. Russian President Vladimir Putin has positioned the BRICS summit as a counterweight to the West.