A US navy attack submarine has docked in a Philippine port close to the disputed shoal where Philippine and Chinese ships are locked in a standoff, a spokesman for Manila's navy said Tuesday.

The USS North Carolina arrived at Subic Freeport on Sunday for "routine ship replenishment," said Philippine Navy spokesman Lieutenant Colonel Omar Tonsay.

"This has nothing to do with that matter," he said, referring to the Scarborough Shoal, claimed by both Manila and Beijing, which have each posted non-military ships in the area for more than a month to assert their claims.

Scarborough is about 234 kilometres (145 miles) west of Subic Bay, a huge former US naval base that the Philippines has converted into a freeport, resort and light industrial zone since US forces left.

The standoff at the shoal began when China blocked an attempt by the Philippines on April 8 to arrest Chinese fishermen who were allegedly taking government-protected marine species from the area.

China claims almost all of the South China Sea, nearly up to the coasts of its Asian neighbours.

This includes Scarborough Shoal, which sits about 1,200 kilometres southeast of the nearest major Chinese land mass, according to Filipino navy maps.

The Philippines insists it has sovereignty over the shoal because it falls within its 200-nautical-mile exclusive economic zone.

Taiwan, Brunei, Vietnam and Malaysia also claim parts of the South China Sea, which is believed to sit atop vast oil and gas resources, making the area one of Asia's potential military flashpoints.

The conflict has grown increasingly tense with Chinese state media once warning that the country was prepared to go to war.

The Philippines has sought to bring the conflict to international tribunals but is also seeking support from its main defence ally, the United States.

The USS North Carolina was due to leave Subic on Saturday, Tonsay said.

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