Philippine authorities are scrambling to contain the country's worst oil spill, which has polluted protected marine areas and ruined the livelihoods of thousands of fishermen.

The Philippines is appealing for international help to contain a spreading oil spill in Guimaras Strait, in the central Philippines.

The tanker, Solar I, was carrying about two million liters of oil when it sank in bad weather last week. It has created an oil slick that is now 30 kilometers long and 30 meters wide.

Lieutenant Commander Joseph Coyme, spokesman for the Philippine Coast Guard, says unless the tanker is removed from the sea it will continue to damage marine life. But the Philippines, he says, does not have the capability to recover a vessel from some 900 meters underwater.

"We are calling on international groups, if they have this equipment, to salvage the vessel, or at least stop the remaining oil [from spreading],"Coyme said. " It would really help a lot to mitigate the environmental impact in this area."

Local efforts have so far been limited to deploying oil spill containment booms. Coyme says strong currents in the area are making containment harder.

The oil spill has ruined the livelihoods of thousands of fishermen on Guimaras Island. It has also damaged mangroves, coral reefs and other protected marine life at the Taklong Island Marine Reserve on the southern tip of Guimaras.

Albert Gaitan heads the Igang Bay Marine Station of the Southeast Asian Fisheries Development Center on Guimaras. He says the oil slick could threaten his group's conservation efforts.

"If this oil spill reaches our area, like the floating cages where we have valuable fin fish being cultured and also the abalone and giant clams project, this will greatly affect our research for sure," he said.

Authorities say it could take at least a year to clean up the spill.

In a separate incident on Tuesday, a Japanese supertanker in the Indian Ocean spilled 4,500 tons of crude oil after a collision with a cargo vessel.