China's fishery administration said on Sunday it had started regular patrols of the South China Sea, sending two vessels to take over from two others currently escorting Chinese fishing boats in the area.

"China Yuzheng 301 and 302 take over from China Yuzheng 311 and 202, which have been patrolling the sea area of Nansha Islands since April 1," said Wu Zhuang, director of Administration of Fishery and Fishing Harbor Supervision for South China Sea under the Ministry of Agriculture.

He said the patrol ships were sent to escort Chinese fishing boats in the South China Sea and reinforce China's fishing rights of the waters around Nansha Islands.

The two ships set sail from Sanya, a coastal city in China's Southernmost Island Province of Hainan, on Sunday.

China's patrol vessels escort the country's fishing boats and help treat fishermen who fall ill, Wu said.