South Korean President Yoon Suk Yeol said a South Korean delegation would visit Ukraine this week to share information on North Korean troop deployment to Russia and discuss cooperation measures.

The president shared the plan during a phone call with North Atlantic Treaty Organization (NATO) Secretary General Mark Rutte, who confirmed that North Korean troops had been deployed in Kursk region, the Yonhap news agency of the Republic of Korea reported.

"I hope that under Secretary General Rutte's leadership, NATO will redouble efforts to monitor and block illegal exchanges between Russia and North Korea in solidarity and coordination," Yoon was quoted as saying.

Yoon said the South Korean delegation is set to brief the EU Political and Security Committee on Tuesday, and then visit Ukraine to meet with intelligence and defense officials to share battlefield information and discuss cooperation measures.

In a second phone call with Yoon in a week, Rutte said the involvement of North Korean forces in the Ukraine war is a "top priority" for NATO and expressed hope for continued discussions on countermeasures and information sharing related to the conflict.

"It is a grave situation where the actual deployment of North Korean troops to the front lines in Ukraine could happen sooner than expected," Yoon was quoted as saying.

South Korea and the United States have said North Korea sent around 3,000 troops to eastern Russia, with Seoul's spy agency expecting about 10,000 soldiers to be deployed by December.

"This unlawful military cooperation between Russia and North Korea fundamentally undermines the rules-based international order and poses a threat to peace on the Korean Peninsula and globally," Yoon said.

Yoon called for the immediate withdrawal of North Korean troops and the cessation of military cooperation between Moscow and Pyongyang, vowing to explore "practical response measures" with the EU and its member countries.

"We will take phased measures depending on the developments in Russia-North Korea military cooperation," he said.

Last week, Yoon said Seoul could consider providing arms to Ukraine, in a possible shift from its policy of only sending humanitarian aid.