North Korea on Saturday tested what appeared to be a submarine launched ballistic missile in the Sea of Japan, the South Korean defense ministry said.

North Korea on Saturday tested what appeared to be a submarine launched ballistic missile in the Sea of Japan, the South Korean defense ministry said.

"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 defense ministry spokesman said.

"We are keeping close tabs on the North Korean military and maintaining a full defense 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.