North Korea has performed a successful missile test from a submarine, reaching an important milestone in its nuclear weapons programme.
The display of technical capabilities of the isolated communist nation prompted international criticism with neighbouring South Korea urging Pyongyang to stop the programme.
Some analysts believe the country, subject to UN sanctions, is trying to develop a nuclear device small enough to be mounted on a ballistic missile, but it is not clear whether it has already achieved its goal.
As some of North Korea’s submarines are technically capable of coming within range of the US mainland, the latest test would make it theoretically possible for North Korea to attack the US, which it considers its utmost enemy together with South Korea with which it is still at war.
South Korea warned on Monday that its rival could build a fully operational submarine equipped with ballistic missiles within two or three years, much faster than the international community expected.
However, some experts believe that despite the obvious progress, North Korea is still years from becoming a serious threat.
During the test, the missile travelled 150m parallel to the sea surface, mimicking the first stage of a guided flight before it would potentially follow an arched trajectory towards a pre-defined target.
The major drawback for North Korea to develop a fully operational system would be its aging fleet of Soviet era submarines lacking advanced tracking equipment for precise guidance.
"They need to build a new, bigger submarine," said Yang Uk, a senior research fellow at the Korea Defence and Security Forum and a policy adviser to the South Korean navy.
North Korea’s submarines capable of carrying missiles are believed to be able to reach Japanese waters. Japan and the USA both reserve rights to conduct pre-emptive strikes on North Korean missile sites if a nuclear attack is viewed as imminent. Launching missiles from submarines could enable Pyongyang to hide them.
"While North Korea's submarines are not especially effective, the challenge of finding even a small number of specific submarines armed with missiles would be quite a challenge," said Jeffrey Lewis of the California-based Monterey Institute of International Studies.
Lewis further added that the missile North Korea tested probably has a range of roughly 2,400 km, which would require a submarine to be at sea for 60-90 days.
"That means a journey to bring the US in range would be pretty daring."
A South Korean defence ministry official who declined to be identified said photographs released on Saturday by the North showing a missile launched from the sea appeared to be authentic.