KYIV, Ukraine, Oct 29, 2024 (BSS/AFP) - Ukrainian President Volodymyr Zelensky said Tuesday he had discussed the deployment of North Korean troops to aid Russia with South Korea's president, Yoon Suk Yeol, and agreed to strengthen security cooperation.

The call between the leaders came as concern among Ukraine's allies is mounting over the apparent transfer of thousands of North Korean soldiers to Russia to bolster Moscow's invasion efforts.

"We discussed the involvement of North Korean military forces in Russia's invasion of Ukraine. The conclusion is clear: this war is becoming internationalised, extending beyond two countries," Zelensky wrote on social media.

President Yoon meanwhile described the North Korean troop transfer as "unprecedented and dangerous" and urged "close communication and counteractions going forward".

Zelensky and Yoon, according to readouts of the call from their offices, confirmed that South Korea and Ukraine would send delegations to each other's countries to deepen security and intelligence cooperation.

Yoon, according to his office, said South Korea would continue to back peace "while working with allies to explore additional cooperation measures for the people of Ukraine".

News of the leaders' telephone call came just after North Korean Foreign Minister Choe Son Hui arrived in Russia for an official visit.