Workers with shovels and rakes were scraping up a thick layer of black sludge that washed ashore from the tanker. Some birds, their feathers caked with oil and unable to see, blundered onto a nearby road and were crushed under vehicles.

The storm killed three seamen. A new storm on Tuesday grounded helicopters searching for five sailors still missing.

Russian Prime Minister Viktor Zubkov said the narrow Kerch Strait, between the Black Sea and Azov Sea, had seen the "biggest mass sinking of ships in the history of modern Russia".

On the orders of Russian President Vladimir Putin, Zubkov travelled on Tuesday to Kavkaz, a port near the border with Ukraine from where the clean-up operation is being coordinated. He also met Ukrainian Prime Minister Viktor Yanukovich.

"The results of our work today and the prosecutors' conclusions will become a serious lesson for the future," Zubkov told rescue workers. "The reason for the tragedy was inclement weather but you probably cannot heap all the blame on that."

"We need to establish: either this was something unavoidable, or it was tardy and inadequate actions by our services, or it was the Russian habit of leaving things to chance," said Zubkov, who also inspected an oil-clogged beach.

Officials say some ships ignored a storm warning at the weekend and put to sea. The sunken tanker was over 30 years old, was not designed for rough seas and did not have a double hull -- a feature many countries insist on to prevent oil spills.

TOXIC CARGO

The Volgoneft-139 tanker released about 2,000 tonnes of its cargo of fuel oil when it broke up. A local spokeswoman for the Russian Emergencies Ministry said a special ship was trying to pump out another 2,000 tonnes of oil still in the tanker's hull.

Fuel oil is a syrup-like liquid which in cold weather sinks to the bottom of the sea, making it hard to clean up.

"More than 600 people are working along the coast," said spokeswoman Tatyana Kobzarenko. "Yesterday and today we collected about 160 tonnes of rubbish contaminated with fuel oil from coastal sites."

Alexander Tkachyov, governor of the Black Sea Krasnodar region, said on Monday the spill was an ecological catastrophe.

Dead and dying seabirds could be seen all along the coast.

"I have heard estimates that 30,000 (birds have died) and these estimates do not seem to be too high," said Vasily Spiridonov, a coordinator with conservation group WWF.

"A significant amount of oil is likely to be at the bottom of the sea ... Most likely it will be brought out by storms onto the shores and the pollution will continue."

Russian meteorologists said winds during Sunday's storm had reached 30 metres (100 feet) per second, speeds that are usually only recorded once in a century.