China is helping look for a missing US sailor in the South China Sea, the country's defense ministry confirmed on Thursday.

The Chinese guided-missile frigate Liuzhou, which was near the area on duty, is assisting the search operation after a sailor was reported missing from a US Navy destroyer about 100 nautical miles southwest of Huangyan Island on Tuesday.

The Defense Ministry said China's assistance was based on the Code for Unplanned Encounters at Sea and humanitarian spirit.

Japan Maritime Self-Defense Force destroyer Sazanami and helicopter carrier Izumo are also involved in the search, according to the US Pacific Fleet.