North Korea tests 'underwater nuclear weapon system'

SEOUL, Jan. 19 (UPI) -- North Korea tested an "underwater nuclear weapon system" in the East Sea, its state media reported Friday, claiming it was a response to this week's joint maritime exercise held by the United States, South Korea and Japan.

According to a report in Korean Central News Agency, the test involved the "Haeil-5-23" system, which appears to be the latest version of the nuclear-capable underwater attack drones that Pyongyang unveiled last year. The report did not specify the date of the test.

"Our army's underwater nuke-based countering posture is being further rounded off and ... will continue to deter the hostile military maneuvers of the navies of the U.S. and its allies," an unnamed spokesman for the North's Defense Ministry said in a statement carried by state-run KCNA.

The USS Carl Vinson nuclear-powered aircraft carrier and naval forces from South Korea and Japan held trilateral drills from Monday to Wednesday in the wake of a North Korean hypersonic missile launch.

The ministry spokesman slammed the maritime exercise as "reckless military confrontation hysteria" and said it "seriously threaten[s] the security of the DPRK."

The Democratic People's Republic of Korea is the official name of North Korea.

Pyongyang has regularly condemned joint U.S.-South Korea exercises as rehearsals for an invasion.

North Korea tested its underwater nuclear drones in March and April, claiming the weapons can create a "super-scale radioactive tsunami through an underwater explosion."

The latest test comes as tensions continue to climb on the Korean Peninsula, with North Korean leader Kim Jong Un calling earlier this week for a constitutional change declaring the South its "primary enemy state and invariable principal enemy."