Kim Jong Un oversees delivery of tactical ballistic missile launchers

The launchers have been described by state media as a modern tactical attack weapon personally designed by Kim and ready to be transferred to Korean People's Army units on the frontier with the South.

North Korea said it test-fired a new tactical ballistic missile last month.

"We believe (the missile launchers) are intended to be used in various ways, such as to attack or threaten South Korea...Deploying near the border would mean that the range is not long," Lee Sung-joon, spokesperson for South Korea's Joint Chiefs of Staff, told a media briefing.

In a speech, Kim blamed the United States for creating a "nuclear-based military block" that forced his country to further strengthen its military capabilities.

North Korea has long condemned joint drills between the United States and South Korea as a rehearsal for invasion.

A spokesperson for Seoul's unification ministry handling inter-Korean affairs said North Korea's illegal nuclear and missile programmes were the primary threat to peace and stability on the Korean peninsula.

Pyongyang will have enhanced nuclear readiness in the near future to deter nuclear threats and protect itself, Kim was quoted as saying in the speech to troops and military scientists.

Kim's daughter, Kim Ju Ae, attended the event, KCNA photos showed, making her first public appearance in nearly three months. South Korean lawmakers said last month she was being trained to become the next leader.

North Korea's state media has reported on her public activities, but not on her political future.