Systems tested also included a mobile short-range anti-aircraft missile system, the Korean Central News Agency (KCNA) reported.

The tests took place Monday, Tuesday and Wednesday, as part of regular efforts to develop and upgrade weapons systems, KCNA said.

South Korea's military earlier said that North Korea had fired multiple short-range ballistic missiles in two rounds on Wednesday, and an "unidentified projectile" the previous day.

According to KCNA, the exercises "confirmed that the surface-to-surface tactical ballistic missile Hwasongpho-11 Ka tipped with the cluster bomb warhead can reduce to ashes any target covering an area of 6.5 - 7 hectares".

Also tested were an "electromagnetic weapon system" and "carbon fiber sham bombs scattering" that KCNA described as "special assets of strategic nature."

The Japan Coast Guard also said Wednesday that an object suspected to be a ballistic missile had been launched from North Korea.

Analysts said the launches, North Korea's fourth and fifth known ballistic missile tests this year, signalled its latest rebuff of Seoul's attempts to repair ties with the North.

Those included an expression of regret from Seoul on Monday over civilian drone incursions into the North in January.

The comments were initially described as "very fortunate and wise behaviour" by Kim Yo Jong, the powerful sister of North Korea's leader.

But on Tuesday, a senior North Korean official described the South as "the enemy state most hostile" to Pyongyang, reviving a label previously used by leader Kim Jong Un.

The launches were Pyongyang's message to Seoul that its anti-South stance remains firm despite Seoul's repeated overtures, said Lim Eul-chul, an expert on North Korea at Kyungnam University.