North Korea claims it tested nuclear-capable underwater drone

North Korea claimed Friday to have tested a nuclear-capable underwater drone designed to generate a gigantic "radioactive tsunami" that would destroy naval strike groups and ports. Analysts were skeptical that the device presents a major new threat, but the test underlines the North's commitment to raising nuclear threats.

The test this week came as the United States reportedly planned to deploy aircraft carrier strike groups and other advanced assets to waters off the Korean Peninsula. Military tensions are at a high point as the pace of both North Korean weapons tests and U.S.-South Korea joint military exercises has accelerated in the past year in a cycle of tit-for-tat responses.

Pyongyang's official Korean Central News Agency said the new weapon, which can be deployed from the coast or towed by surface ships, is built to "stealthily infiltrate into operational waters and make a super-scale radioactive tsunami through an underwater explosion" to destroy enemy naval strike groups and ports.

The report came hours before South Korean President Yoon Suk Yeol pledged to make North Korea pay for its "reckless provocations" as he attended a remembrance service honouring 55 South Korean troops killed during major clashes with the North near their western sea border in past years.

Simulated attacks

The testing of the purported "nuclear underwater attack drone" was part of a three-day exercise that simulated nuclear attacks on unspecified South Korean targets, which also included cruise missile launches Wednesday.

KCNA said the North's latest tests were aimed at alerting the United States and South Korea of a brewing "nuclear crisis" as they continue with their "intentional, persistent and provocative war drills." It said the tests were supervised by North Korean leader Kim Jong-un, who vowed to make his rivals "plunge into despair."

The U.S. and South Korea completed an 11-day exercise Thursday that included their biggest field training in years, and are preparing another round of joint naval drills that will reportedly involve a U.S. aircraft carrier.

Hours after the North Korean report, South Korea's air force released details of a five-day joint aerial drill with the United States that began Monday and concluded Friday above waters off South Korea's western coast, which included live-fire demonstrations of air-to-air and air-to-ground weapons.

The air force said the exercise, which involved various South Korean fighter jets and at least one U.S. A-10 attack plane, was aimed at verifying precision strike capabilities and reaffirming the credibility of Seoul's "three-axis" strategy against North Korean nuclear threats preemptively striking sources of attacks, intercepting incoming missiles and neutralizing the North's leadership and key military facilities.

The North Korean drone is named "Haeil," a Korean word meaning tidal waves or tsunamis. The North's Rodong Sinmun newspaper published photos of Kim smiling next to a large, torpedo-shaped object at an unspecified indoor facility, but didn't identify it.

Other photos published with the same article showed sea-surface tracks supposedly caused by the drone's underwater trajectory and a pillar of water exploding up into the air, possibly caused by what state media described as an underwater detonation of a mock nuclear weapon carried by the drone.

KCNA said the drone was deployed Tuesday off the North's eastern coast, travelled underwater for nearly 60 hours, and detonated a test warhead at a target standing for an enemy port. It said the test verified the operational reliability of the drone, which it said the North has been developing since 2012 and tested more than 50 times in the past two years, although the weapon was never mentioned before in state media until Friday.

Kim Dong-yub, a professor at Seoul's University of North Korean Studies, said that it's impossible to verify North Korea's claims about the drone's capabilities or that it had tested the system dozens of times. But, he said, the North is intending to communicate that the weapon has enough range to reach all South Korean ports.