Japan plans to develop unmanned underwater vehicles to lay and sweep mines, aiming to attain maritime superiority in the event of a contingency near the country's southwestern Nansei Islands chain, a source close to the matter said Monday.

The plan comes as the Defense Ministry seeks to ramp up the use of drones to support missions of the ground, maritime and air branches of the Self-Defense Forces.

File photo taken Aug. 8, 2022 shows the Defense Ministry in Tokyo. (Kyodo) ==Kyodo

It is expected to be articulated in the National Security Strategy and two other key defense documents slated to be revised by the end of this year.

Along with artificial intelligence, drones are considered a game-changing technology in contemporary warfare. They are seen as effective in reducing casualties in combat while being able to destroy adversaries' war-fighting assets at a relatively low cost.

The ministry's weapons procurement arm, the Acquisition, Technology and Logistics Agency, is already producing an underwater drone that can detect mines while avoiding obstacles autonomously. The agency expects to start research and development at an early date on a model that can lay and remove mines.

The newly developed drones are aimed at deterring adversaries from landing on the Nansei Islands, as well as sweeping mines during maritime blockades, including when important sea lanes are blocked, the source said.

The island chain stretches southwest from Kagoshima Prefecture to Okinawa Prefecture. The islet group includes the Japanese-controlled, Beijing-claimed Senkaku Islands, which China calls Diaoyu, in the East China Sea.

Currently, SDF vessels and planes are used to lay mines, but such mines could be removed if adversaries track the vessels and planes via satellite and other means to estimate where they laid the mines.

With underwater drones, the government hopes the SDF will be able to lay mines without running such risks while at the same time making it difficult for adversaries to contemplate invasion using vessels and submarines.

Besides underwater drones, the government plans to acquire small aerial drones to attack invading enemies. The ministry has requested funding for the acquisition in a new budget from April.

The government is also considering developing unmanned fighters to support the country's next-generation fighter jets.