North Korea on Saturday claimed it tested this week a second known type of nuclear-capable underwater attack drone designed to destroy naval vessels and ports, adding to a flurry of weapons demonstrations this year that have heightened tensions with rivals. The report of the four-day test came a day after the nuclear envoys of the United States, South Korea and Japan met in Seoul to discuss the growing North Korean nuclear threat and called for stronger international efforts to crack down on illicit North Korean activities funding its weapons programme.

The North’s official Korean Central News Agency said the drone, named “Haeil-2” after a Korean word meaning tsunamis or tidal waves, travelled underwater for more than 71 hours before successfully detonating a mock warhead in waters near the eastern port city of Tanchon on Friday. KCNA said the test proved that the weapon could strike targets 1,000 kilometres (621 miles) away with “fatal attack ability.”