SEOUL, South Korea — North Korea unveiled for the first time a nuclear-powered submarine under construction, a weapons system that can pose a major security threat to South Korea and the U.S.

North Korean leader Kim Jong-un inspected a project to build a nuclear-powered submarine, warning that his country's maritime defense capability will be "fully" projected "in any necessary waters without limitation.

The announcement came amid fears that Pyongyang may be receiving crucial military technology from Russia in return for sending troops and weapons for its war against Ukraine.