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 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.

The US and South Korea are said to be 'closely analysing' the latest missile tests from North Korea, which the hermit state said are part of an 'overall plan to implement efforts to build the country'

Pyonyang said the tests were carried out "as part of an overall plan to implement efforts to build the country's defence capabilities".

North Korea has test-fired sea-to-surface strategic cruise guided missiles, the North's state media reported Sunday, in the first missile launch since US President Donald trump took office last week.

North Korea carried out missile tests on Saturday in the latest act of defiance from the hermit kingdom, which has been ramping up its military activity in recent months

North Korea's foreign ministry vowed the "toughest counteraction" against the United States as long as Washington "refuses" the country's sovereignty.

North Korea says it tested a cruise missile system, its third known weapons display this year, and vowed “the toughest” response to what it called the escalation of U.S.