A stricken oil tanker laden with 20 million gallons of fuel oil broke in two and sank today in the Atlantic Ocean off Spain's northwestern coast, raising fears of an ecological disaster larger than the Exxon Valdez spill if the oil's containers split open on the ocean floor.

The Prestige, a Greek-managed ship sailing under a Bahamian flag, had already lost about 2.5 million gallons of highly toxic fuel oil from a 50-foot-wide crack that opened in its hull during a storm last Wednesday, and from sinking today about 150 miles off the coast of Spain's Galicia region. The crew was airlifted to safety before the ship sank.

The ship's containers appeared to be intact, but shipping experts and environmentalists said it was only a matter of time before they burst, either from damage caused by falling 11,800 feet and hitting the ocean floor or from rusting. "It's a time bomb at the bottom of the sea," Maria Jose Caballero of the environmental group Greenpeace told the Associated Press.

The Prestige was carrying almost twice the 11 million gallons of Alaskan crude that was lost by the tanker Exxon Valdez off the coast of Alaska in 1989. That spill contaminated 700 miles of coastline, according to Greenpeace.

There was some hope that the low temperatures at the bottom of the Atlantic might keep the tanks intact and solidify the fuel oil to prevent it from spreading. Pumping out the oil for salvage at a depth of more than two miles would be extremely difficult.

Before the ship went down, salvage workers trying to save it had been battling unseasonably high winds that produced 16-foot waves.

The oil spill has already caused havoc on Spain's normally pristine Galician coast, with thick dark sludge washing up on beaches, thousands of birds and fish caked in oil and the region's fishing industry, known for its lobster, brought to a halt.

Fuel oil is heavier and more toxic than crude oil, and more difficult to clean up.

The ship's loss produced a new round of finger-pointing and recrimination in European capitals, with some officials blaming the European Union for not taking tougher action against aging vessels such as the Prestige. EU officials in Brussels and in Strasbourg, France, countered that governments could take the initiative themselves.

Under EU rules scheduled to take effect in July, 25 percent of all ships would be inspected before entering EU ports, and ships flying flags of convenience would be singled out for inspection. Also under the new rules, all single-hull tankers, deemed less safe than double-hull ships, would be phased out by 2015, beginning with the older ones. Other single-hull vessels would still be allowed.

The new rules were put in place after a similar disaster off the French coast in December 1999, when the tanker Erika dropped about 2.8 million gallons of oil. Both the Prestige and the Erika were built in Japan during the shipbuilding boom of the mid-1970s, and experts said ships of that vintage are now showing the stress of age. The Prestige was built in 1976.

Today's disaster brought calls for the new regulations to be implemented sooner than the EU will require. But any change is likely to be vigorously opposed by the shipping industry, which feels that the older vessels have complied with existing rules and are subject to regular inspection, and that banning them immediately would place an unfair financial burden on the industry.

French President Jacques Chirac fired the first salvo in the blame game, telling reporters today, "I am horrified by the inability of those in charge -- politically, nationally and particularly at the European level -- to take action which permits these ships, which are fit only for the dustbin, to carry on."

Chirac told reporters that the time had come to "urgently take draconian measures," without specifying what they would be.

In Strasbourg, the EU transportation commissioner, Loyola de Palacio, said individual European governments could move on their own to toughen the regulations on tankers, without waiting for the EU-wide rules to take effect. She wrote to EU leaders today urging them not to wait until the July deadline to begin enforcing the stricter rules.

In Spain, Deputy Prime Minister Mariano Rajoy was quoted by news agencies as saying during a tour of the Galicia coastline that the Spanish government would move quickly on a measure to allow only double-hull tankers to enter Spanish ports.

Two women inspect a beach in Baranan, Spain, where fuel oil from the stricken tanker Prestige washed ashore.