A new Chinese attack submarine is the first submarine in the world to feature an important enhancement to its stealth qualities: an oddly-shaped sail, or conning tower.

China, which claims Taiwan as part of its own territory, is believed to have developed a submarine able to escape medium-frequency sonars.

The head of the domestic submarine programme Admiral Huang Shu-kuang told reporters last week that the goal was to fend off any attempt from China to encircle Taiwan for an invasion or impose a naval blockade. It would also buy time until US and Japan forces arrive to aid Taiwan's defence, he added.

China's Type 039C Yuan-class submarine appears to mark a new era in underwater stealth technology, posing significant challenges to traditional dete