Meanwhile the European Union's transport commissioner said, after surveying the damage, she would ask EU ministers as early as next month to slap a ban on single-hulled tankers like the Prestige.

Spain says 10,000 to 11,000 tonnes of the viscous fuel toxin spewed out before the storm-damaged Prestige broke in half and sank on Tuesday some 130 nautical miles off the coast where the ocean is some 3.6 km (two miles) deep.

Environmental group Greenpeace estimates 20,000 tonnes leaked from the tanker, which was carrying 77,000 tonnes of fuel oil - twice the amount that spilled when the Exxon Valdez ran aground in Alaska in 1989 to create what has been stamped in the world's mind as the worst ever oil spill.

A wave of oil slicks continued to menace Spain and Portugal and France said last week that maritime pollution units had been put on alert and volunteers mobilised amid fears that strong winds would blow oil to its coast.

DESOLATE SIGHT ON BEACHES

At Doninos, a picturesque beach 40 km (25 miles) from La Coruna and the northernmost point the slick has reached so far, thick lumps of tar washed up on the beach overnight.

"This is a disaster for people who make a living from fish and shellfish," said Antonio Fereiroa, a worker at a beachside cafe.

Spain has deployed more than 500 workers to scrape oil off nearly 400 km (250 miles) of coastline where fishing has been banned.

"They've sent a handful of men to clean up a bit," Fereiroa said. "Resources are short everywhere and in some places there's nowhere to throw away the oil people are picking up."

Rajoy said experts told the government the oil inside the ship would solidify in the frigid ocean depths but that the French submarine - a small scientific research craft - would take a closer look just in case.

Other experts say oil tanks inside the shattered hull could have ruptured on impact or could eventually rust through and release their contents into the ocean.

The Portuguese navy reported sighting a new oil slick about 50 metres wide last week where the tanker went down, a spokesman for the navy's Hydrographic Institute said. Another three of the same size or slightly bigger were sighted on Thursday.

The government's representative in Galicia, Arsenio Fernandez de Mesa, said there was a slick five miles wide by six or seven miles long where the ship went down, but there was no evidence it was growing.

"Everything depends on the winds. Now they are blowing from the southwest and west and this spill is going north," he said.

CRITICISM MOUNTS AS SLICK SPREADS

The initial cleanup cost was pegged at 42 million euros ($42 million) with the bill certain to rise. The Spanish government last week also approved 200 million euros in credit lines for people and business affected by the disaster.

The central government also added 10 euros a day to the 30 euros the regional government in Galicia is offering to fishermen while they are out of work.

Meanwhile pressure grew in Europe to move forward a ban on single-hulled tankers like the Prestige and tighten inspections.

There are still more than 5,000 single-hulled oil and chemical tankers registered in the world, out of a total fleet of 7,300 tankers. Newer, double-hulled tankers are less likely to spill their cargo if they have a collision.

European Union Transport Commissioner Loyola de Palacio told a news conference in the Galician capital Santiago that she would press EU ministers on December 6 to pass a decree banning the transport of heavy fuel oil in single-hulled ships. (Additional reporting by Joelle Diderich and Ian Simpson).