Timeline: North Korea’s nuclear weapons programme

South Korea called the action “very serious and concerning” and urged Pyongyang to immediately stop developing submarine-launched ballistic missiles (SLBMs), which it said hindered regional security.

North Korea is already placed under a number of UN sanctions for its missile and nuclear tests, and is believed to be trying to develop a nuclear device small enough to be mounted on a ballistic missile.

The brutal regime’s submarine fleet, like much of its military, is based on Soviet-era technology and the country is still some way from developing any missile system of submarine that could threaten its sworn enemy – the United States.

North Korea’s test appears to have been successful in getting a missile launched from under the sea’s surface. There is a further challenge in submarine missile technology North Korea will need to overcome – getting the missile on an arched trajectory so it can head towards its target.

One South Korean defence official said North Korea could have fully operational, ballistic-missile armed submarines within five years.

The missile travelled around 150 metres, a South Korean official said.

North Korea’s state controlled news agency KCNA, the mouthpiece of Kim Jong-un’s regime, said the missile test showed North Korea has a “world-level strategic weapon capable of striking and wiping out in any waters the hostile forces infringing upon the sovereignty and dignity of Songun Korea”.