China will set up new civilian patrols with a 5,000-tonne vessel in the disputed South China Sea, state-run media said on Tuesday, in another move that could inflame territorial disputes.

Beijing claims much of the waters and has put a vast swathe of it under the administration of Sansha city, in the contested Paracel islands, which also hosts a military garrison.

Local authorities will "provide a 5,000-tonne patrol vessel at Sansha and gradually set up a system of three regular patrols", China Ocean News reported, citing an agreement between the city and the island province of Hainan, which oversees it.

The intent was to "safeguard national sovereign rights and benefits, develop at-sea assistance, ensure navigational safety" among other reasons, the report said.

Even minor moves by China that appear to assert territorial claims can provoke a regional reaction, as the Asian giant is engaged in disputes with several neighbours, including an escalating row with Japan over islands in the East China Sea which has raised fears of unintended conflict.

Portions of the South China Sea are also claimed by the Philippines, Vietnam, Malaysia, Brunei and Taiwan.

Earlier this month both the US and Philippines criticised a law approved in Hainan in November reaffirming an existing requirement that foreign fishing vessels obtain permission to enter its waters.

China also declared in November an Air Defense Identification Zone over parts of the East China Sea -- including the islands disputed with Japan -- provoking vehement condemnation from Tokyo and Washington.

Aircraft entering the zone were required to identify themselves and maintain communication with Chinese authorities.