North Korean state media, meanwhile, reported that Kim Jong Un visited the Russian Embassy in Pyongyang to extend congratulations.
Thursday's launch may have tested the performance of weapons Pyongyang intends to export, according to the South Korean military.
The parade came a week after Moscow and Pyongyang confirmed that North Korean troops were deployed to the Kursk region.
Experts say Pyongyang's first-ever long-endurance warship, named Choe Hyon, was likely built with Russian assistance.
Pyongyang unveiled the 5,000-ton destroyer-class vessel named Choe Hyon over the weekend.
Pyongyang had recently unveiled its new warship, a 5,000-tonne destroyer-class vessel named Choe Hyon.
Pyongyang this week confirmed for the first time that it had sent troops to help Russia recapture parts of the Kursk region from Ukrainian forces.
Moscow and Pyongyang until now had responded vaguely to the South Korean and Western claims of the troop deployment.
Moscow and Pyongyang until now had responded vaguely to the South Korean and Western claims of the troop deployment.
Moscow and Pyongyang until now had responded vaguely to the South Korean and Western claims of the troop deployment.