The European Union and South Korea have called for the immediate withdrawal of North Korean troops from Russia.

EU foreign policy chief Josep Borrell met with South Korea's Defense Minister Kim Yong-hyun and Foreign Minister Cho Tae-yul in Seoul on Monday.

Cho and Borrell later released a joint statement condemning North Korea for transferring arms and deploying troops to Russia. It said such moves constitute a "serious breach" of international law and threaten the security of the world.

Cho and Borrell called on North Korea and Russia to immediately cease "unlawful" military cooperation and withdraw North Korean troops from Russia.

They also said the EU and South Korea will closely monitor what Russia provides to the North, in return for its provision of arms and military personnel.

The head of Ukraine's Center for Countering Disinformation, Andriy Kovalenko, said on social media on Monday that the first batch of troops from North Korea has already come under attack in the western Russian region of Kursk.

But Kovalenko did not give further details, and there have been no official statements from either Ukraine's military or its presidential office so far.

US Secretary of State Antony Blinken on Thursday said as many as 8,000 North Korean troops were deployed to the Kursk region. He said he was expecting them to engage in combat in the coming days.