North Korea has successfully test-fired a submarine-launched ballistic missile (SLBM), a news report said.Pictures circulating in country's media showed North Korean leader Kim Jong-un looking towards a missile shot out of water. The picture also showed red lettering on the side of the missile, which read as "bukgeungsong," meaning "north star" or "polaris".According to a report by a Xinhua news agency, Kim Jong-un hailed the newly developed missile as a "world-level strategic weapon." It quoted the North Korean leader saying that the Korean military now possess a "world-level strategic weapon capable of striking and wiping out in any waters the hostile forces that infringe upon Korea's sovereignty and dignity."

The report stated that the test was carried out by a sub that dived to launch depth on the sounding of a combat alarm.

"After a while, the ballistic missile soared into the sky from underwater," the agency reported.

A fully-developed SLBM capability would take the North Korean nuclear threat to a new level, allowing deployment far beyond the Korean peninsula and the potential to retaliate in the event of a nuclear attack.

Earlier this year, satellite images had revealed the conning tower of a new North Korean submarine, which according to US analysts appeared to house one or two vertical launch tubes for either ballistic or cruise missiles.

These analysts had also said at the time that developing an operational SLBM capability would cost a lot and it would take "years" for North Korea to achieve that.

Dan Pinkston, Korean expert at the International Crisi Group said, "If this is what North Korea claims it is, then it has come much sooner than anyone expected."

"An SLBM capability would certainly increase the credibility of the North's retaliatory threat, but I'd like to see what foreign intel says about this test," he added.

While it not hidden that the North has been running an active ballistic missile development programme, expert opinion is split about its progress.

There have also been contrasting opinions on whether the North has acquired ability to miniaturize a nuclear device that would fit onto a delivery missile.

Last year in September, the Defence Ministry of South Korea cited intelligence reports that Pyongyang was perceived to be developing a vertical missile launch tube for submarine use.

The Ministry officials reported that the North's 3,000-tonne Golf-class submarine could be modified to fire medium-range ballistic missiles.

In 2012, North Korea launched a satellite into orbit, which was condemned by the international community as a disguised ballistic missile test that led to tightening of UN sanctions.

This latest test of submarine launching ballistic missile was reportedly termed as an "eye-opening success," which was at a par with the 2012 satellite launch.