North Korea has tested a new nuclear-capable underwater attack drone, state media reported on Friday, as leader Kim Jong Un warned South Korea and the United States to cease their joint military exercises.
During the test, the new North Korean drone sailed underwater at 80 to 150 metres (260-500 feet) for over 59 hours and detonated a non-nuclear payload in waters off its east coast on Thursday, North Korean state news agency KCNA claimed.
Experts think North Korea is showing off its more diversified nuclear threats to Washington and Seoul, though they are unconvinced whether the undersea vehicle is ready for deployment.
North Korea seeks to indicate "to the United States and South Korea that in a conflict, the potential vectors of nuclear weapons delivery that the allies would have to worry about and target would be vast," said Ankit Panda, a senior fellow at the U.S.-based Carnegie Endowment for International Peace.
"There would be silos, railcars, submarines and road-mobile missile launchers. And now they're throwing in this undersea torpedo," he continued.
On Monday, the isolated country flew a short-range missile from an underground silo, a departure from conventional basing tactics. Called "Haeil", or tsunami, the new drone technology is meant to make surprise attacks in enemy waters and destroy navy strike groups and important operational ports by creating a big radioactive wave by an undersea explosion, the KCNA reported.
"This underwater nuclear assault drone can be launched at any shore and port or pulled by a surface ship for operation," the news agency reported, adding that Kim oversaw the test.
A South Korean military official said they were assessing North Korea's allegations. Under the condition of anonymity, a U.S. official stated that there was no evidence of a nuclear test.
Uncertainty exists about whether North Korea has fully developed the miniaturized nuclear warheads required for its smaller weapons. Experts say mastering such warheads would likely be a priority if the North resumes atomic testing.
A photo issued by state media showed Kim beaming next to an oversized torpedo-shaped item but did not identify it as the new drone. Additional photographs revealed the object's underwater journey and visible explosions on the top of the water.
According to Panda, the operational concept of the weapon is similar to that of Russia's Poseidon nuclear torpedoes, a new category of retaliatory weapon designed to create destructive, radioactive blasts in coastal areas.
North Korea also confirmed it had fired cruise missiles on Wednesday to practice carrying out tactical nuclear attacks, confirming earlier reports from the South Korean military.
According to KCNA, the cruise missiles had a "test warhead resembling a nuclear bomb" and flew between 1,500 and 1,800 kilometres (930 and 1,120 miles). The newest tests took occurred as South Korean and U.S. troops conducted their largest amphibious landing manoeuvres in years, featuring a U.S. amphibious assault ship, on Monday.
North Korea stated that military exercises by the United States and South Korea necessitate its forces to "prepare for all-out war and prioritize the quality and quantity of its nuclear force."
Pyongyang has long objected to South Korean and American military exercises, claiming they are preparations for an invasion of the North. South Korea and the United States assert that the activities are strictly defensive and have condemned North Korea's tests as destabilizing and violating United Nations sanctions.
On Thursday, the allies ended 11 days of their usual springtime drills, termed Freedom Shield 23, but have other field training activities continuing.
North Korean leader Kim expressed "his will to make the U.S. imperialists and the South Korean puppet regime plunge into despair for their choice," KCNA said, adding that he warned the enemies that they should stop reckless anti-North Korea war drills.
The director of the U.S. Defense Intelligence Agency stated on Wednesday that it does not appear that North Korean leader Kim will conduct a nuclear test during U.S.-South Korea military exercises, but the United States will remain vigilant.