South Korea yesterday said it was "closely watching" preparations by Russian President Vladimir Putin for an expected visit to its arch-foe North Korea.
North Korea and Russia are both under international sanctions, and have deepened ties since the latter invaded Ukraine in 2022.
North Korea has been accused of providing arms to Russia for its war in Ukraine, allegations the Kremlin has branded as "absurd".
Neither side has confirmed an itinerary for Putin's expected visit.
"The government is closely watching President Putin's preparations for his visit to North Korea," South Korea's foreign ministry said.
"Exchange and co-operation between Russia and North Korea should be conducted in a way that contributes to peace and stability on the Korean Peninsula while complying with the Security Council resolutions," it added.
The Kremlin told Russian state-run media last month that a visit was "being prepared".
A Pentagon report last month said Russia is using North Korean ballistic missiles in Ukraine, citing debris analysis.
Experts have said that during Putin's expected visit, North Korea would likely push to export more war materials to be used in Ukraine, in exchange for importing food and energy from Russia.
Earlier yesterday, a senior official in the South Korean president's office said Putin was expected to visit North Korea "in a few days".
The official said Putin's visit to the North would take place around the same time as a meeting between South Korean and Chinese officials in Seoul.
That meeting is due to take place early next week, according to South Korea's Yonhap news agency.
North Korean leader Kim Jong Un on Wednesday hailed his country's ties with Russia, according to state media.
Ties between North Korea and Russia have "developed into an unbreakable relationship of comrades-in-arms", Kim wrote in a message to Putin carried in the official Korean Central News Agency.
Their "meaningful" ties will "further consolidate the eternal milestone" in the new era, Kim added, according to KCNA.
Kim made a rare overseas trip to meet Putin in Russia last year.
At the time, he said the North's ties with Moscow were his country's "number one priority".
The US and South Korea have accused North Korea of supplying weapons to Russia for use in Ukraine, in violation of UN sanctions, in return for help with its space programme.
Analysts have also warned that ramped-up testing and production of artillery and cruise missiles by the nuclear-armed North could be in preparation for shipments to Russia for use in Ukraine.
North Korea is barred by UN sanctions from any tests using ballistic technology, but Moscow used its UN Security Council veto in March to effectively end UN monitoring of violations, for which Pyongyang has specifically thanked Russia.
