China has revealed it is developing a top secret underwater drone designed to track and destroy enemy submarines with no human input.

The unmanned attack robot was first test fired in the Taiwan Strait a decade ago but its existence was not made public until now.

The project to build the drone was funded by the People's Liberation Army and dates back to the 1990s, reports the South China Morning Post.

Under testing, it was reportedly able to detect a dummy submarine, identify its origin and hit it with a torpedo.

The craft is said to rely entirely on artificial intelligence and does not need any instructions from an operator.

Details of the part-declassified project were revealed in an academic paper last week.

Researchers described a 2010 test in the Taiwan Strait in which a drone was programmed to follow a pre-set course around 30ft below the surface.

When its sonar detected another craft, the drone changed course and circled the target, using onboard sensors to gather readings which were analysed by its computer.

It then fired autonomously and hit the dummy submarine with an unarmed torpedo.

Professor Liang Guolong, who led the team, said that with more advanced technology the drones would be able to hunt in packs.