North Korea stages 'tactical nuclear attack' drill

North Korea conducted a simulated "tactical nuclear attack" drill on Saturday that included two long-range cruise missiles, state media reported on Sunday, as leader Kim Jong Un inspected shipbuilding and munitions factories.

The KCNA news agency said the drill was carried out early on Saturday to "warn enemies" that the country would be prepared in case of nuclear war as Pyongyang again vowed to bolster military deterrence against Washington and Seoul.

The two cruise missiles carrying mock nuclear warheads were fired towards the West Sea of the peninsula and flew 1,500km at a preset altitude of 150m.

A separate statement said Kim visited Pukjung Machine Complex, which produces marine engines, and a major munitions factory to stress the importance of strengthening Pyongyang's naval forces.

"He affirmed that a future plenary meeting of the Central Committee of the WPK (Worker's Party of Korea) would set forth an important modernisation of the complex and the development direction of the shipbuilding industry," the KCNA statement said.

The statement did not specify the date of his visit.

The latest missile test came just after the joint annual summertime exercises between South Korea and the US, known as Ulchi Freedom Shield, came to a close on Thursday after an 11-day run, featuring air drills with B-1B bombers.

North Korea has been stepping up its military deterrence against Washington and Seoul and has criticised last month's summit agreement between the two on improving military cooperations.

A KCNA statement on Aug 21 said Kim recently visited a navy fleet stationed on the east coast to oversee a test of strategic cruise missiles aboard a warship, and stressed the ship would maintain striking power for combat situations.