BEIJING (BLOOMBERG) - China renewed its protests over US spy planes entering what it claims as territory after the commander of the US Pacific Fleet joined a surveillance flight over the disputed South China Sea.

"For a long time, US military ships and aircraft have carried out frequent, widespread, and up-close surveillance of China, seriously harming bilateral mutual trust and China's security interests, which could easily cause an accident at sea or in the air," the Ministry of Defence said in a statement published by state-run People's Daily.

Admiral Scott Swift joined a seven-hour surveillance mission on a P-8A Poseidon plane on July 18 to witness the aircraft's full range of capabilities, the US Pacific Fleet said on its website.

China claims more than 80 per cent of the South China Sea, where it has been engaged in an accelerated program of reclamation around artificial islands it's created in the Spratly chain. Five other countries claim features in the waters, home to some of the world's busiest shipping lanes.

China is "entitled to the surveillance over related airspace and sea areas so as to prevent maritime and airspace accidents and situations that could harm China's national security," China's Foreign Ministry said May 22.

The Chinese navy issued eight warnings to a US P8-A Poseidon conducting surveillance flights over the islands in May. US Defence Secretary Ashton Carter said in response that the US would fly and sail wherever international law allowed.

Pacific Command didn't says whether the P-8 aircraft with Swift on board flew over the islands that China claims.