North Korea tests submarine-launched missile: South Korea

"North Korea launched a projectile which was believed to be a submarine-launched ballistic missile (SLBM) around 6:30 pm (0930 GMT) in the East Sea (Sea of Japan) near the northeastern port of Sinpo", a defence ministry spokesman said.

"We are keeping close tabs on the North Korean military and maintaining a full defence posture", he said.

It was not immediately known whether the launch was a success, he added.

North Korea has been pushing to acquire SLBM capability that would take its nuclear strike threat to a new level, allowing deployment far beyond the Korean peninsula and the potential to retaliate in the event of a nuclear attack.

It has conducted a number of what it says were successful SLBM tests, but experts question the claim, suggesting Pyongyang had gone little further than a "pop-up" test from a submerged platform.

The test-firing comes as North Korea gears up for a rare and much-hyped ruling party congress early next month, at which leader Kim Jong-Un is expected to take credit for pushing the country's nuclear weapons programme to new heights.

Numerous analysts have suggested the regime might carry out a fifth nuclear test as a display of defiance and strength just before the congress opens.

Tension has been high on the divided Korean peninsula since Pyongyang's fourth nuclear test in January and rocket launch a month later that was widely seen as a disguised ballistic missile test.

The UN Security Council responded by imposing its strongest sanctions to date over the North's nuclear weapons programme.

Pyongyang has responded by staging a series of short- and mid-range missile tests and claiming a series of significant technical breakthroughs in its nuclear strike capability.

It claimed it had miniaturised a nuclear warhead to fit on a missile and successfully tested an engine designed for an inter-continental ballistic missile that could reach the US mainland.