Police in the southern Chinese island province of Hainan will board and search ships which enter into what China considers its territorial waters in the disputed South China Sea, state media said.

The South China Sea is Asia's biggest potential military trouble spot with several Asian countries claiming sovereignty.

Chinese fishing boats sail in the lagoon of Meiji reef off the island province of Hainan in the South China Sea. Credit:AP

From January 1, Hainan police will have the authority to board and seize control of foreign ships which "illegally enter" Chinese waters and order them to change course or stop sailing, the China Daily reported.

"Activities such as entering the island province's waters without permission, damaging coastal defence facilities and engaging in publicity that threatens national security are illegal," the English-language newspaper said.