North Korea on Friday claimed to have tested an underwater system capable of delivering nuclear weapons.

State media said the system, known as Haeil-5-23, is currently under development.

North Korea used the term “Haeil’’ to describe underwater attack drones, which it claimed can also be equipped with nuclear warheads.

Pyongyang did not say when the test took place.

The rogue state is subject to tough international sanctions due to its nuclear weapons programme.

The test was reportedly carried out in response to a joint naval exercise involving South Korea.

The U.S. and Japan took place from Monday to Wednesday in international waters south of the South Korean island of Jeju.

North Korea had accused the three countries of provocation.

Pyongyang said it would continue to develop its underwater systems until they were complete.

Last year, the country reported tests with nuclear-capable underwater drones.

It also spoke of secret weapons.

North Korea has significantly increased the scale of its missile tests over the past two years and stepped up its rhetoric against the U.S. and South Korea.

The two countries have expanded their military cooperation in response to Pyongyang’s rhetoric. 

(dpa/NAN)