North Korea said it has conducted another test of its “underwater nuclear attack drone,” the second time the system has ever been mentioned in public. The strategic weapons test comes after a flurry of joint war games by Washington and Seoul, prompting Pyongyang to cut off a joint communication line with the South. 

On Monday, the state-run Korean Central News Agency (KCNA) issued a statement saying the DPRK carried out a test of its “Haeil-2” weapon, an underwater drone which can be equipped with a nuclear warhead, according to the military, which previously claimed the system could produce a “radioactive tsunami.” The exercise began on April 4 and ran for three days. 

“The test perfectly proved the reliability of the underwater strategic weapon system and its fatal attack ability,” KCNA reported. “The system will serve as an advantageous and prospective military potential of the armed forces of the DPRK essential for containing all evolving military actions of enemies, removing threats and defending the country.”

Pyongyang carried out the test as Washington, Seoul and Japan conducted anti-submarine war games in the waters near the Korean Peninsula. Prior to the trilateral military exercises, US and South Korean forces conducted the largest war games in the region in five years, and plan to stage another massive round of live-fire drills in June.

North Korea issued a strong response to the drills, albeit under the guise of an unsigned KCNA editorial. “The US and its followers should never forget the fact that their rival state has possessed the nuclear attack capability in practice as well as the characteristics of the people and army of the DPRK which do not make empty talk,” the article said, adding “It will be quite clear how the DPRK’s nukes will be used if the war deterrence does not work on those who are running amok.”

As tensions have spiked, Seoul has reached out to Pyongyang through a joint communication line. However, South Korea said its calls have gone unanswered for four consecutive days. A spokesperson for Seoul said it is the first time since October 2021 that the two states had gone more than a day without communicating.

Go Myong-hyun, a senior fellow of the Asan Institute for Policy Studies, told the Miami Herald, that Pyongyang likely cut the line as a response to the American and South Korean war games. “It’s unlikely a step toward escalation, but more of a tit-for-tat response against the joint military drills and much more elevated deterrence posture from South Korea and the US,” Go said.

While the US and its allies claim their war games are defensive, North Korea says the drills are preparations for an invasion aimed at bringing down the regime. “The US has parroted that the military drills with South Korea are defensive,” the KCNA editorial said. “But, they can never conceal with such veils as ‘defensive’ and ‘routine’ their aggressive colors as provocateurs and the fact that the current exercises are a deliberate military action prompted by their sinister scheme … to wreck peace and stability in the Korean Peninsula.”