North Korea has launched a submarine capable of firing ballistic missiles, according to South Korean military sources quoted in state media Sunday.

According to a report from Yonhap, South Korean sources said that North Korea had "imported a Soviet-era Golf-class diesel submarine and modified it."

South Korean military officials however, said that Pyongyang has not yet acquired technology to deploy submarine-launched ballistic missiles.

The news comes after U.S.-based North Korea experts revealed that they believed that the reclusive Stalinist state may be testing submarine-based missiles.

38 North, the website of the U.S.-Korea Institute at the Johns Hopkins School of Advanced International Studies, posted satellite images on their website which purport to show a test stand for sea-based ballistic missiles.

"This may be an early indication that North Korea is considering basing ballistic missiles armed with nuclear weapons on submarines in order to hide them and make them more survivable," Joel Wit, the editor of 38 North told CBS News.

According to data compiled by Global Firepower, North Korea actually possesses the largest submarine fleet in the world, with 78 craft, compared with the United States' 72. However, according to Russian news agency RIA, most of North Korea's fleet consists of obsolete Soviet or Chinese vessels. The agency adds that the ability to mount a vertical launching system on a ballistically capable submarine would significantly increase North Korea's naval strength.

In September of this year, North Korea reportedly test-fired three short range tactical missiles off of its east coast, according to a New York Times report. The incident was the latest in a long line of controversial missile and nuclear tests conducted by the country, that have put it at odds with Western powers, and many of its Asian neighbors.