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.

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

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

China's leadership is too "overwhelmed" with its internal problems to consider an invasion of Taiwan, President Tsai Ing-wen said in an interview with the New York Times.