The dispatch of North Korean troops to Russia as Moscow wages war in Ukraine highlights the need for security cooperation between the European Union and South Korea, EU foreign policy chief Josep Borrell said on Monday.

The deployment "regrettably illustrates the importance of our shared security agenda," he said before talks with South Korean Foreign Minister Cho Tae-yul in Seoul. The EU and South Korea are holding their first Strategic Dialogue meeting after Washington and Seoul sounded the alarm about North Korea sending troops to help Russia.

Borrell also met South Korean Defence Minister Kim Yong-hyun and expressed concern over the development, the South Korean defence ministry said.

"Russia’s aggression against Ukraine is an existential threat," Borrell said in a post on X and also posted a photo of him shaking hands with Kim. "The Republic of Korea is best positioned to understand it. We are united in our support to Ukraine. I encouraged them to step it up."

Borrell said in a post on X on Sunday that he had visited the heavily fortified Demilitarized Zone separating the two Koreas after arriving in South Korea following a trip to Japan, and described the visit as reminder of the need to invest more in peace.

He said in another post that he was visiting South Korea to take security and defence cooperation between the EU and Seoul to "the next level", but gave no further details. Cho said last week that all possible scenarios were under consideration, when asked about whether Seoul could send weapons to Ukraine in response to North Korea aiding Russia.

South Korea has provided non-lethal aid to Ukraine, including mine clearance equipment, but has resisted Kyiv's requests for weapons.

Seoul also sees it as likely that the North will be compensated by Moscow with military and civilian technology, as it races to launch a spy satellite and upgrade its missile capabilities. North Korea last week flexed its military muscle with the test of a huge new solid-fuel intercontinental ballistic missile dubbed Hwasong-19.

Washington expects North Korean troops in Russia's Kursk region, which borders Ukraine, to enter the fight against Ukraine soon, US Secretary of State Antony Blinken said last week.

At talks in Moscow on Friday, North Korean Foreign Minister Choe Son Hui said her country intended to back Russia until it achieves victory in the Ukraine war. (Reuters)