Beijing  - China might convert more naval vessels to patrol disputed areas of the South China Sea to counter illegal fishing and "other countries' unfounded territorial claims," state media said Thursday.

China faces new "challenges and complications" in the South China Sea, the official China Daily quoted a senior fisheries official as saying, pointing to recent claims by the Philippines and Malaysia to disputed islands and a standoff with a US naval surveillance ship.

"Faced with a growing amount of illegal fishing and other countries' unfounded territorial claims of islands in China's EEZ [exclusive economic zone], it has become necessary to step up the fishery administration's patrols to protect China's rights and interests," Wu Zhuang, the director of fisheries supervision for the South China Sea, told the newspaper.

"China will make the best use of its [retired] naval ships and may also build more fishery patrol ships, depending on the need," Wu said.

Last week, China sent its largest and fastest fisheries ship, the Yuzheng 311, to patrol the disputed Paracel and Spratly Islands, known in China as the Xisha and Nasha islands, respectively.

Foreign Affairs Ministry spokesman Qin Gang on Tuesday reiterated China's claim to "indisputable sovereignty over the islands in the South China Sea" within its 3-million-square-kilometre EEZ.

"The Chinese government has always attached importance to fishery administration in the South China Sea, and the Chinese fishery patrol boat is in the South China Sea on a routine fishery administration mission," Qin told reporters.

The Global Times newspaper last week quoted Wu as saying the Yuzheng 311 was the start of a planned expansion of patrols over the next five years.

The converted naval rescue ship was dispatched in response to at least three incidents occurring this month, including a US surveillance ship being blocked by five Chinese vessels off southern China's Hainan island.

Malaysian Prime Minister Abdullah Ahmad Badawi visited two reefs on the Spratly Islands on March 5 to claim them as Malaysian territory.

Last week, Philippine President Gloria Macapagal Arroyo signed into law a bill defining the country's territorial boundaries and laying claim to areas that included the Spratlys and the nearby Scarborough Shoal, or Huangyan islands.

Part or all of the two island groups are also claimed by Taiwan, Vietnam and Brunei while the Paracel Islands are claimed by Vietnam. (dpa)