Kim Jong-un emphasises military strengthening amid recent North Korean missile tests

"Bolstering naval forces is presently the utmost priority for a credible defence of our country's maritime sovereignty and to intensify war preparations," said Kim, as cited by North Korea's KCNA news agency.

State media reported that the North Korean leader had visited the port city of Nampcho to survey the new warship constructions.

On Friday morning, Greenwich Time, the South Korean military reported the detection of "several unidentified manoeuvring missiles" on North Korea's western coast. The data collected is still under review by the army.

This represents another act of provocation from North Korea in the past month. In mid-January, the military performed tests on underwater drones capable of carrying nuclear weapons, followed by supersonic missile tests with medium and long-range capabilities in early January.

As the AFP agency recalls, last year, North Korea declared that its navy possessed its first nuclear-powered submarine. However, South Korean experts are doubtful whether this unit is actually in active service. Last Sunday's missile test, which intended to launch manoeuvring missiles from a submarine, underscores the emphasis on developing a submarine fleet in North Korea.