The drills were led by the South Korean navy’s 2nd and 3rd fleets, which focused on building operational readiness in their respective theaters and preparing for various naval threats, the service said.

It comes after the first official acknowledgement by Pyongyang and Moscow of North Korean troops' involvement in the Ukraine war.

South Korea’s spy agency says an estimated 4,700 North Korean soldiers have been killed or wounded while fighting alongside Russia against Ukrainian forces