A South Korean official says that North Korea has launched a new submarine capable of firing ballistic missiles.

A government source in Seoul said Sunday that the North recently launched a new submarine after importing and modifying a Soviet-era Golf-class diesel submarine which was built in 1958 and decommissioned in 1990.

Pyongyang is known to have imported the vessel in the early 1990s.

Experts at home and abroad have raised the possibility of the North’s development of such submarines, but it is the first time that a South Korean official has confirmed it.

The source said that the North's new vessel is what the website 38 North reported last month as “an unidentified submarine” citing satellite imagery.

The North is believed to have developed a submarine equipped with the vertical launch system, which is six years ahead of South Korea.

The South Korean military plans to deploy three 3,000-ton submarines equipped with the vertical launch system from 2020 to 2024 and three additional ones from 2025 to 2030.