China's official news agency says two lighthouses have started operating on a reef on a disputed island chain in the South China Sea, amid rising concerns among the U.S. and China's neighbors about Beijing's maritime ambitions.

Xinhua News Agency says the Ministry of Transport held a completion ceremony Friday for the 50-meter-high (164-foot-high) Huayang and Chigua lighthouses on Huayang Reef in the Spratly Islands, which are mostly barren islands, reefs and atolls that are believed to be atop oil and natural gas deposits. They also straddle one of the world's busiest sea lanes.

The Spratlys are also claimed by Taiwan, Malaysia, the Philippines, Vietnam and Brunei.