North Korea is developing bases for its fleet of assault hovercraft that will be able to deploy elite special forces troops on South Korean soil in half an hour.

The rogue state is building two new bases and upgrading two existing facilities for the vehicles on its west coast, increasing the threat to South Korean-held islands in the West Sea.

The additional bases are expected to be completed next year, with analysts pointing out that the new site at Yonbong-ni will house the furthest forward-deployed assault hovercraft in the North Korean fleet.

While many navies around the world have units of the amphibious craft in their armouries, they are primarily used on a smaller scale and for specialist missions.

North Korea, however, began introducing hovercraft into its strike forces in the 1980s, replacing conventional landing craft that were seen as too slow and unable to carry sufficiently large loads to carry out a successful invasion.

Satellite images taken in December show work under way at the Yonbong-ni base, which covers nearly 170 acres, including the construction of hardened shelters for 54 hovercraft, according to a study printed in Beyond Parallel, produced by the Center for Strategic and International Studies.