North Korea has unveiled for the first time a nuclear-powered submarine under construction.

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.

North Korean leader Kim Jong Un inspected a project to build a nuclear-powered submarine, state media reported Saturday, saying that "radically" boosting the navy was a key part of Pyongyang's

North Korea condemned an upcoming U.S.-South Korea joint military exercise Friday, saying that "counteraction is inevitable" and warning that the allies would "pay dearly."

North Korea criticised on Friday annual joint military drills planned by the United States and South Korea, saying it will worsen the situation on the Korean Peninsula, state media KCNA said.

The South Korean military said the accident near the North Korean border occurred during training ahead of Freedom Shield, an annual U.S.-South Korea joint military exercise.