Filipino sailors hold the line at flashpoint West Philippine Sea reef

SOUTH CHINA SEA, undefined — Sailors aboard two Philippine Coast Guard boats crashed through West Philippine Sea waves, shadowed by Chinese vessels as they attempted to bring desperately needed supplies to colleagues holed up on a ship inside a remote ring of reefs.

The coast guard's BRP Teresa Magbanua has been anchored inside Sabina Shoal since April to assert Manila's claims to the area off its coast and prevent China from seizing it.

But the Filipino sailors on board the ship are running critically low on food and other provisions -- which Monday's tense "humanitarian" mission by two smaller coast guard boats was intended to supply.

Philippine and Chinese vessels have collided twice this month near Sabina Shoal, located 140 kilometers (86 miles) from the Philippines' western island of Palawan and 1,200 kilometers from China's nearest major landmass Hainan island.

AFP journalists on board one of the 44-meter (144-foot) Philippine resupply boats watched as Chinese coast guard and navy ships shadowed both vessels for hours, eventually surrounding them.

With 40 Chinese ships in their path in rough seas, the Philippine Coast Guard turned back, leaving the sailors on the 97-meter Teresa Magbanua without fresh provisions.

Sabina Shoal is the latest reef to become a flashpoint in decades of maritime disputes between the Philippines and China.

In 1995, Beijing began building structures on Mischief Reef, which Manila claims as part of its continental shelf, and China has since constructed several artificial islands that it uses as military outposts.

More recently, the focus of clashes between Philippine and Chinese vessels has been Second Thomas Shoal, about 30 kilometers southeast of Mischief Reef.

A handful of Filipino troops are stationed on a rusty navy ship that the Philippines deliberately grounded there in 1999 to check China's advance.

A Filipino sailor lost a thumb in a clash there in June, when Chinese coast guard members wielding knives, sticks and an axe foiled a Philippine Navy attempt to resupply its troops.

Beijing and Manila reached a "provisional arrangement" in July for the delivery of necessities and rotation of Filipino troops at Second Thomas