The massive oil leak from a tanker that capsized off the Philippines' Oriental Mindoro province last month has reached one of the country's' marine reserves and sanctuaries, the Philippine Coast Guard (PCG) said on Monday.

PCG Batangas station commander Captain Victorino Acosta said the oil slick was sighted on Monday morning in the Verde Island Passage between Batangas province and the northeastern tip of Mindoro island, reports Xinhua news agency.

The area is a body of water with the highest concentration of coastal fishes, corals, crustaceans, molluscs, sea grasses and mangroves, which is described as one of the global centres of marine biodiversity.

It is also home to endangered and threatened species, including the critically endangered hawksbill turtle, whale sharks, manta rays, dugongs, humphead wrasses, giant groupers and giant clams.

Verde Island Passage is also a favourite spot for divers attracted by the "wall" of beautiful corals, sea fans and anemones billowing in constantly moving water.

The MT Princess Empress was carrying 800,000 liters of industrial oil when it sank off Oriental Mindoro on February 28, causing a widespread oil spill in Oriental Mindoro and the neighbouring areas.

The ill-fated oil tanker was sailing to Iloilo province in the central Philippines from Bataan province, northwest of Manila when it experienced engine trouble and sank.

According to government data, the spill affected nearly 152,000 residents in 131 villages.

Dozens of people have also fallen ill.

Pola town in Oriental Mindoro is the most affected of the nine municipalities of Mindoro province.

Pola town official Lysander Fetizanan told a forum that the disaster has affected the livelihood and the environment of the town people.

"(The sea disaster) has affected our way of life and living," Fetizanan said.