North Korea has tested a new nuclear-capable underwater attack drone that can generate a radioactive tsunami, state media reported on Friday, as it blamed joint military drills by South Korea and the U.S. for raising tensions in the region.

During the drill, the new drone cruised underwater at a depth of 80 to 150 meters for over 59 hours and detonated in waters off its east coast on Thursday, North Korean state news agency KCNA said.

Dubbed Haeil, or tsunami, the drone system is intended to make sneak attacks in enemy waters and destroy naval striker groups and major operational ports by making a superscale radioactive wave through an underwater explosion, the KCNA said.