Nearly 500 birds covered in the toxic goo have already been recovered for treatment in La Coruna, the main port city in the affected region of Galicia.
Up to another 10,000 may have died from the spill, which started washing ashore last Tuesday, according to the WWF/Adena environmental lobby group.
Hundreds of volunteers have been working since the weekend to clear many of the 136 soiled beaches, wearing rubber suits and masks to protect them from contact with the fuel oil, which is laced with sulphur and other toxic chemicals.
Two specialised ships, one from France and one from the Netherlands, were attacking floating patches of oil located off the northern part of Spain's "Coast of Death" -- the stretch of shore above Portugal that runs alongside one of the world's busiest shipping lanes.
It was in that area that the Prestige, a Liberian-registered, Bahamas-flagged ageing tanker carrying 77,000 tonnes of fuel oil, broke in two and sank as it was being towed out to sea after getting into trouble.
Its Greek captain, Apostolus Magouras, said he hit a container from another ship floating in the water, according to a local newspaper, La Voz de Galicia. Spanish authorities were detaining him until the circumstances of the ship's troubles are cleared up.
Most of the oil, about 60,000 tonnes, went down with the ship on November 19. The wreck is lying on the ocean floor 200 kilometres (120 miles) off Galicia.
The Spanish coastal region, boasting a varied and rich marine environment which along with the tourist industry underpins the local economy, has lost an immediate 42 million euros (dollars), according to an early government estimate.
A ban on fishing and mussel harvesting was extended Monday to cover around 500 kilometres (320 miles) of affected coastline.
Compensation of 40 euros a day will be handed to those who depend on the sea for their livelihood and who have been robbed of lucrative Christmas sales. The loss in earnings is a tough blow for a sector that raises 475 million euros a year for the region -- 10 percent of its output.
Another 200 million euros in cheap state loans has been offered, as have tax breaks and easier access to welfare.
That bill will rise if more oil washes ashore, likely well beyond the provision set aside by the Prestige's British insurers, the London Steamship Owners Mutual Insurance Association Limited, also known as the London Club.
The International Oil Pollution Compensation (IOPC) Fund, a body established under the auspices of the International Maritime Organisation, has already made 178 million dollars available to cover compensation claims.
Spain's Deputy Prime Minister Mariano Rajoy, overseeing the crisis, has insisted that the situation is under control.
But the media and environmentalist groups complain that they are being kept in the dark about details of the accident and the clean-up operation.
One of the groups, Greenpeace, says the amount of oil floating off Spain is twice that announced by the government, and contests Madrid's assurance that the remaining oil in the tanker is staying inside the broken hull.
Many of the 600 clean-up volunteers complained that the government was not doing enough to help their painstaking task.
"People are coming and are cleaning up, but we're not getting any supervision from anyone," Lidia Beceiro, a university student, said as she cleared the black muck from the Doninos beach south of La Coruna.
Local authorities "even forbid us to clean up," said another volunteer, Manuela Bustavar, a local pensioner wearing an old grey pullover and rubber boots to protect her from the oil.
"But the young people around here haven't listened to them. They continue to clean up and have brought others into help with the job," she said.
A French mini-submarine was on its way to probe the wreck and determine the state of the oil. Four other oil-pumping ships, from Belgium, Britain and Germany were to arrive over the next two days.
As the country adapted to the crisis, the political storm, both inside and with EU neighbours, was growing.
Spain's opposition Socialist party has demanded the resignation of the head of Galicia's semi-autonomous government, Manuel Fraga.