North Korean leader Kim Jong Un called for bolstering nuclear forces this year during a visit to the country's nuclear material production base and nuclear weapons institute, state media KCNA said on Wednesday.

South Korea 's Yonhap News Agency said North Korea might be using a vertical cold-launch system to fire the missiles. The system, which is commonly associated with submarine- and ship-based weapons, ejects a missile from its container before the missile ignites midair.

North Korea test-fired strategic cruise missiles on Saturday the official Korean Central News Agency reported, marking a third launch this month as Donald Trump returned to power in the US.

North Korea has test-fired sea-to-surface strategic cruise guided missiles, the North's state media reported Sunday, quoting Kim as saying that Pyongyang's deterrence means are being perfected.

North Korea has tested sea-to-surface strategic cruise guided missiles, Pyongyang's state media reported on Sunday. State-controlled KCNA news agency quoted the country's Missile Administration as stating the test-fire,

North Korea conducted a test of strategic cruise missiles from the sea, overseen by Kim Jong Un, KCNA reports. North Korea conducted a test of strategic cruise missiles from the sea on Saturday. This information was reported by the North Korean agency KCNA on Sunday morning local time.