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

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 announced it had performed a test of its cruise missile system on Saturday. It was the communist country’s fourth known missile launch since November and the second in less than a week since President Donald Trump ’s inauguration.

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'

North Korea has test-fired sea-to-surface strategic guided cruise missiles, state news agency KCNA reported Sunday, adding that the weapons "precisely" hit their targets.

North Korea said Sunday that 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.

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.

By Hyonhee Shin SEOUL (Reuters) -North Korean leader Kim Jong Un has called for bolstering nuclear forces this year during a visit to a nuclear material production base and nuclear weapons institute,