MOSCOW — The sinking of a floating oil rig that left more than 50 crew dead or missing is intensifying fears that Russian companies searching for oil in remote areas are unprepared for emergencies — and could cause a disastrous spill in the pristine waters of the Arctic.

Only four months ago, Russian energy giant Gazprom sent Russia's first oil platform to the environmentally sensitive region, and industry experts and environmentalists warned it is unfit for the harsh conditions and is too far from rescue crews to be reached quickly in case of an accident. They are demanding Russia put Arctic oil projects on hold.

Russia is the world's largest oil producer, but it extracts most of its oil onshore, with no more than 2 percent of its production coming from mature offshore fields in the warm Black and Caspian seas and relatively new fields just off Sakhalin Island in the far east.

As Russia's core oil fields in Eastern Siberia are depleted, companies are looking north. The government hopes that up to 80 million tons of oil will be produced annually in the Arctic by 2030.

Russia is trying to assert jurisdiction over parts of the Arctic, which is believed to hold up to a quarter of the Earth's undiscovered oil and gas. By speeding up the Arctic oil project, the government is strengthening its bid.

The Kolskaya floating oil rig that capsized and sank in the Sea of Okhotsk on Dec. 18 had done exploratory drilling for Gazprom Neft Shelf, a subsidiary of Gazprom. It was being towed back to an eastern Russian port in a fierce storm when a strong wave broke some of its equipment and portholes, and it capsized in the choppy water.

Gazprom is now pioneering the oil development of Russia's sector of the Arctic and was the first Russian company to dispatch a drilling rig to the Pechora Sea in northwest Russia.

Russian oil companies have never operated in weather conditions as harsh as those found in the ice-bound Arctic, where ice ridges are meters (yards) deep and storms are frequent. The Kolskaya accident has reinforced fears that they are unprepared to meet the challenges.

"This tragedy has once again reminded us of how high the risks of offshore accidents are," said Alexei Knizhnikov, an oil and gas policy officer with the World Wildlife Fund.

WWF, Greenpeace and five regional Russian environmental organizations signed a petition on Thursday calling for a parliamentary investigation and urging the government to suspend the oil projects for now.

The petition accuses government agencies of failing to enforce environmental and safety regulations and says that current laws are inadequate for dealing with the magnitude of risk in the Arctic.

Environmentalists first raised their concerns when Gazprom announced in August that it was sending its platform to the Arctic for exploratory drilling in the Pechora oil field, which holds some 6.6 million tons of oil.

The platform's underwater section was built in Russia in the 1990s, while its upper part comes from a platform built in Scotland in 1982 and decommissioned from the North Sea in 2002.

Gazprom insists the Prirazlomnaya platform, billed as the first to be ice resistant, is safe and contains no old equipment except for its frame.

"We've done our best to implement the latest technology and regulations to prevent any accidents," Vladimir Vovk, chief of Gazprom's department for the management of equipment and technologies in developing marine fields, said at a news conference in September.

Environmentalists question both the state of the equipment and the platform's design. Because the Prirazlomnaya is situated hundreds of kilometers (miles) offshore, it is designed to store huge quantities of oil until tankers can arrive to collect it. The platform's storage tanks can hold up to 120,000 tons (840,000 barrels).

Unlike the Kolskaya, which was carrying no oil when it sank, the Arctic platform could potentially cause a disastrous spill if it capsized in icy, rough seas.

The distance from shore would also complicate any rescue or cleanup mission. The nearest port of any size is in Murmansk, some 1,000 kilometers (600 miles) away.

Even in warmer, more hospitable waters, accidents at oil platforms have been disastrous.

A giant oil slick was approaching the coast of Nigeria on Friday after what Royal Dutch Shell said was a spill during the transfer of oil from its floating platform in the offshore field to a waiting tanker. The spill came less than a week after Shell received approval from the U.S. government to drill exploratory wells off Alaska's northwest coast, in the Chukchi Sea near Russian waters.

In the Gulf of Mexico, the 2010 explosion of the BP-operated Deepwater Horizon rig killed 11 workers and led to more than 200 million gallons (4.8 million barrels) of oil spewing from a well deep beneath the sea.

Russia's parliament gave preliminary approval in September to a bill intended to tighten regulations on oil companies working in the Arctic.

Yekaterina Khmelyova, an environment law officer at the WWF, said the bill does not do enough to hold the oil companies publicly accountable or to guarantee a full assessment of the environmental risks. She said environmentalists and the business community are working on a new draft that among other things would provide for the creation of clean-up funds.

Oil industry experts also have expressed doubts about Gazprom's expertise in offshore drilling in the Arctic as well as the platform's design.

They have questioned the economic justifications for the project. The oil in the Pechora field is of low quality and the project will be loss-making without tax breaks, said Valery Nesterov, a senior analyst with the Moscow-based investment bank Troika Dialog. For state-controlled Gazprom, the Arctic project appears to be more of strategic importance than about any immediate economic benefits, he said.

"This is clearly a strategic task that the company is executing," Nesterov said. "It looks like Russia is not going to give up that strategy since the interests of ship yards, machinery producers and, possibly, the military are involved."

Four years ago, Russia staked its claim to supremacy in the Arctic by planting a titanium flag on the ocean floor and arguing that an underwater ridge connected the country directly to the North Pole. The United States does not recognize the Russian assertion and has its own claims, along with Denmark, Norway and Canada.

Russia, Canada and Denmark are planning to their respective file claims to the ridge to the United Nations.

In past years, Russian ship yards and machinery producers have been able to stay afloat largely thanks to large orders coming from state-owned plants and government-sponsored projects. A large-scale oil and gas development of the Arctic is likely to give a welcome boost to both industries.