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.