North Korean leader Kim Jong-un says the country should be ready to conduct nuclear attacks at any time to deter war, accusing the United States and South Korea of expanding joint military drills involving American nuclear assets.

Kim’s remarks on Monday came as the isolated country conducted what KCNA called nuclear tactical exercises meant to send strong warnings against the allies.

In the exercises, a ballistic missile equipped with a mock nuclear warhead flew 800 kilometres before hitting a target at the altitude of 800 metres under the scenario of a tactical nuclear attack, KCNA said.

South Korea and Japan reported a launch of a North Korean short-range ballistic missile off the east coast on Sunday, the latest in a series of missile tests in recent weeks.

North Korea has reacted furiously to South Korea-US combined military drills, calling it a rehearsal for invasion against it. The allies have been carrying out their annual exercises since earlier this month.

In another dispatch, KCNA said more than 1.4 million North Koreans have volunteered to join or re-enlist in the military to fight against Seoul and Washington, up from some 800,000 reported by a state newspaper two days before.

– AAP