North Korea is building two new submarines, including one capable of firing ballistic missiles, a South Korean lawmaker said Tuesday, following a closed-door briefing by the South's National Intelligence Service.

North Korea has a large submarine fleet but only one known experimental submarine capable of carrying a ballistic missile.

"One of the submarines North Korea is building can carry a submarine-launched ballistic missile (SLBM)," said Ha Tae-keung, an opposition party lawmaker on parliament’s intelligence committee. "One is a modified Romeo Class and the other is a new medium-large size one."