An oil spill in waters just half a mile off Ecuador's Galapagos Islands grew worse on Sunday, threatening some of the world's rarest land and sea animals and birds, officials said.

``It is a disaster,'' Environmental Ministry spokesman Mauro Cerbino told Reuters. "It may be one of Galapagos' worst disasters."

A damaged vessel, the Ecuadorean-registered Jessica, ran aground on Tuesday near the archipelago's main port, on its easternmost island of San Cristobal. The Jessica was on its way to service a private tour boat operator and Petrocomercial, an arm of the state oil company that provides the islands with fuel.

The spill has already affected animals including sea lions, pelicans and several other species of birds in the islands, administered by Ecuador and located 600 miles off the coast in the southern Pacific Ocean.

Adm. Gonzalo Vega, director of Ecuador's merchant marine in Guayaquil, said on Sunday that about 144,000 gallons of diesel and bunker, a heavy fuel used by tour boats that operate in Galapagos, had spilled into the sea.

As much as 96,000 gallons of fuel remained aboard the ship, though crews were working to remove the tanks to avoid future spillage.

The Exxon Valdez supertanker dumped 11 million gallons of oil into the Alaskan seas when it ran aground in 1989.

Some Of Shore Affected

"With the movement of the waves, part of the islands' shores have been affected, and the rest has gone out to the open sea," Vega told Reuters on Sunday, adding that the ship's tilt made recovering the fuel even more difficult. Cerbino said the spill covered close to 390 square miles and mainly affected Santa Fe and San Cristobal islands.

A minor spill began late on Friday when a pipe in the ship's machine room burst. But the serious contamination began early on Saturday, when strong waves spread the diesel and bunker fuel aboard the Jessica.

The half-sunken ship, owned by private company Acotramar, will probably either be crushed or split in two, Vega said, though crews are working to remove the tanks of fuel still on board before this happens.

Cerbino said the ship, relatively small, did not carry the insurance that would have covered the $500,000 it cost the Ecuadorean government to request help from the U.S. Coast Guard in controlling the damage.

He said it went aground because the captain was navigating through shallow waters without a map.

The World Wide Fund for Nature, a global conservation body, called on Sunday for limits to shipping off the Galapagos, which British naturalist Charles Darwin visited in 1835 while developing his theories of national selection.

Isolated Species

The islands are home to hundreds of species, including giant tortoises, that have evolved for thousands of years in isolation and with little human intervention.

The Swiss-based WWF warned in a statement that the spill could have deep and lastingly affect the islands' creatures.

Private fishing operators and Ecuador's marine service have been working since Friday to control the spill, fencing in the fuel and applying chemicals to neutralize its impact, and a team of experts from the U.S. Coast Guard arrived on Sunday to help remove fuel from the ship.

Local residents tried to prevent the spill from reaching the islands' shores, while the Galapagos National Park Service and the Charles Darwin Research Station struggled to protect threatened wildlife.

The WWF said it was crucial for the Ecuadorean government and the international shipping community to consider designating the waters around the Galapagos as a particularly sensitive sea area.

Sian Pullen, the body's respected shipping specialist, said such measures would help ensure a much higher level of protection for a unique part of the world. Environmentalists say that keeping clear of the islands, which lie across shipping routes from the western coast of Central and South America, would add at most two days to travel time to Australia and Indonesia but that shipping companies had been reluctant to accept the extra cost.