South Korea's intelligence agency has suggested that some of North Korea's military units including generals dispatched to Russia may have moved to the battlefield to fight against Ukraine.

The National Intelligence Service briefed parliamentary members on its analysis on Tuesday.

A lawmaker who attended the briefing cited the agency as saying Russia's military was teaching its terminology to North Korean soldiers. But agency officials said the two sides appeared to be struggling with communication.

The briefing addressed a recent report that North Korea's Foreign Minister Choe Son Hui was heading to Russia for an official visit.

The agency said the visit is likely aimed at discussing Pyongyang's additional dispatch of troops and compensation for them.

Agency officials also assessed the North's unsuccessful launch of a military reconnaissance satellite in May.

They said preparations are apparently underway for another attempt through military cooperation with Russia.

The officials said they will continue monitoring in light of Pyongyang's possible seventh nuclear test after next week's US presidential election.