South Korea and Ukraine have stepped up warnings that North Korea is preparing to send troops to support Russia’s war on Ukraine in a sign of deepening military cooperation between Moscow and Pyongyang.

Speaking to reporters in Brussels on Thursday, Ukrainian President Volodymyr Zelenskyy said Pyongyang is preparing to send 10,000 troops. NATO Secretary-General Mark Rutte promptly dismissed the assessment, saying there was no evidence North Korean soldiers are involved in the fight.

South Korean President Yoon Suk Yeol convened an emergency security meeting Friday to discuss the latest development, with a statement from his office calling it "serious security threat” to South Korea and the international community.