A Chinese fishing boat has run aground on a World Heritage-listed coral reef in the Philippines, roughly 1,600 kilometres (1,000 miles) from China's nearest major landmass, authorities said Tuesday.

The vessel, with 12 crew members, was found stranded in the shallows of Tubbataha Reef in the Sulu Sea just before midnight on Monday, coast guard spokesman Lieutenant Commander Arman Balilo told AFP.

"This is a small fishing boat, but we are wondering how they strayed into Tubbataha. Apart from illegal entry, we are investigating them for possible poaching as well," Balilo said.

Balilo said the boat was to be pulled off the reef on Tuesday and then towed to the nearby island province of Palawan, where the fishermen would be detained and questioned by authorities.

Balilo said Chinese fishermen frequently strayed into Philippine waters, but this was the first time in recent years that they had been detected as far south as Tubbataha.

The grounding of the vessel comes as the Philippines and China are locked in a bitter dispute over competing territorial claims to the South China Sea.

China claims nearly all of the sea, even waters approaching the coasts of the Philippines, Vietnam and other countries in Southeast Asia.

The Philippines accused China of occupying a shoal, which is home to a rich fishing ground, near its main island of Luzon last year. The Philippines has asked a United Nations panel to rule that China's claims are invalid.

However Tubbataha reef is in the Sulu Sea, which is further southeast and not claimed by China. The Sulu and South China seas are separated by Palawan, one of the Philippines' biggest islands.

The reef is about 1,600 kilometres southeast of Hainan island, China's nearest major landmass.

Balilo said he did not want to speculate how the Chinese fishermen reached Tubbataha.

But one navy official told AFP the fishermen likely sailed through the South China Sea and then a narrow strait at the southern tip of Palawan.

Tubbataha is famous among divers around the world for its walls of coral and diverse marine life that many say rival that of Australia's Great Barrier Reef. Sailing in the Tubbataha park is illegal without a permit.

However a US Navy minesweeper also ran aground on Tubbataha in January, and salvage crews had to break it down in pieces in a delicate operation that only ended on March 29.

Philippines authorities estimate that the USS Guardian damaged at least 2,345 square metres of the reef and are seeking 58 million pesos ($1.4 million) in compensation.