South Korea's military confirmed Sunday it has detected signs of North Korea's development of a submarine-based ballistic missile launch system.

In a report to an opposition lawmaker, the Joint Chiefs of Staff (JCS) said there is an indication that the North is developing a submarine-launched ballistic missile (SLBM).

"There is no intelligence yet that North Korea has an SLBM in operation. But the possibility of a North Korean submarine equipped with an SLBM has been detected recently," the JCS said in the document submitted to Rep. Jin Sung-joon of the main opposition New Politics Alliance for Democracy.

South Korea and the U.S. are jointly scrutinizing the North's related move, added the JCS.

A senior South Korean government source also said the South Korean and U.S. intelligence agencies spotted signs that the North has developed a ballistic missile launch tube.

"A missile launch tube for submarine use has been spotted, which appears to have been developed at North Korea's submarine base," the source said on condition of anonymity.

Chances are high that the North will test-fire a SLBM in the foreseeable future, and if it is successful, the communist nation is expected to seek to acquire larger submarines, according to the source.

An annual white paper on warships, Jane's Fighting Ships, said in its 1994 edition that North Korea purchased 40 decommissioned submarines from Russia, including several Golf-class and Romeo-class submarines.

The North has reportedly deployed more than 20 Romeo-class submarines, which are not capable of carrying an SLBM launcher.

It may be modifying 3,000-ton Golf-class submarines for SLBMs, the source said.

In August, a U.S. web magazine, the Washington Free Beacon, quoting unnamed U.S. defense officials, said the U.S. intelligence community has identified at least one North Korean submarine equipped with a ballistic missile launch tube. (Yonhap)