North Korea says it has tested an underwater nuclear weapons system in waters off its east coast. The country says it was in response to the latest joint naval drills by the United States, South Korea and Japan.

North Korea's defense ministry announced the test on Friday in a statement read on the state-run Korean Central News Agency.

The statement said the Academy of National Defense Science carried out an important test of the Haeil-5-23 weapons system, without specifying a date.

It also said the test was in response to three days of joint drills by the US, South Korea and Japan that ended on Wednesday. A US nuclear-powered aircraft carrier, the USS Carl Vinson, also took part in the exercises.

According to the statement, the North Korean "army's underwater nuke-based countering posture is being further rounded off."

It also said "various maritime and underwater responsive actions will continue to deter the hostile military maneuvers of the navies of the US, and its allies."

Twice last year, in March and April, North Korea claimed it successfully detonated warheads at target areas in tests of underwater nuclear-capable attack drones.
The drones were dubbed "Haeil," which means tsunami in Korean.