BEIJING (AFP) — Vast new Chinese barges spotted off the country's south coast could be used to land heavy equipment and thousands of personnel in a possible invasion of Taiwan, defense experts say.

Beijing this week launched what it called "punishing" drills around Taiwan, sending jets and warships in a rehearsal for a blockade and assault on the self-ruled island.

And a memo from United States Naval War College has revealed another potential weapon in Beijing's arsenal — barges that can connect via extendable ramps to form an 820-meter-long pier from deep waters to land.

With retractable legs that can push into the sea floor, the Naval War College said they could create a platform for personnel and "hundreds of vehicles" an hour to land on Taiwan, which China claims as its own territory.

"These barges are clearly meant to facilitate amphibious invasion against Taiwan," Wen-Ti Sung, a nonresident fellow at the Atlantic Council's Global China Hub, told Agence France-Presse.

Wargaming of a potential Chinese invasion of Taiwan long assumed that Beijing's People's Liberation Army would have been forced to rely on small amphibious landing vessels to get ashore.

Only a handful of Taiwan's beaches are suitable for large-scale amphibious landings — giving Taipei a critical edge in the defense of the island.

"These barges may enable Chinese forces to make landings even on the more challenging terrains of the Taiwanese coastline," Sung said.

This, he added, "gives the Chinese military a greater selection of potential landing spots, and spreads Taiwanese defenses thin."

Satellite images from Planet Labs PBC obtained by Agence France-Presse show the system deployed in the waters off Zhanjiang city of Guangdong, southern China, at the end of March.