ISTANBUL >> When a 28-year-old volunteer named Nikolai stepped onto a sandy beach on Russia’s Black Sea coast in a hazmat suit just before New Year’s Eve, he was so overwhelmed by the amount of thick oil film that he almost broke down.

He and other volunteers were tasked with shoveling away the oil-drenched sand, but “the scale is just too big,” he said.

Two weeks into the new year, and four weeks after the spill, Russian President Vladimir Putin acknowledged the extent of the disaster and dispatched senior officials to deal with Russia’s largest oil spill in years, which has befouled some of the country’s most popular beaches.

The oil was released by two aging Russian tankers that were damaged during a heavy storm in the Kerch Strait on Dec. 15. At least 2,400 metric tons of oil spewed into the sea, Russian officials said.

The disaster in the strait, which separates the Crimean Peninsula from mainland Russia, raised questions about whether the vessels were part of the so-called shadow fleet that Russia uses to evade sanctions on its oil industry, sometimes employing ships in shoddy conditions.

One of the vessels, the Volgoneft-212, split in half and sank, killing one crew member. The other, the Volgoneft-239, ran aground near the port of Taman. The two vessels were loaded with a total of 9,000 tons of heavy fuel oil, and authorities are now working not only to clean up the shores, but also to try to contain additional spills from the ship that ran aground.

Russian officials originally claimed that the spill was contained, but soon after the disaster, sightings of floating oil and tarred birds were reported all along Russia’s Black Sea coast.

On Sunday, the government said it was allocating another 1.5 billion rubles (about $15.3 million) to the cleanup effort, drawing the money from its reserve fund. Three days earlier Putin ordered a report on the condition of Russia’s tanker fleet, and also asked a deputy prime minister to review Russian legislation covering oil shipments by sea and river and to look into the “scientific advances on the cleanup of similar disasters,” his press office said.

Last week, the Ukrainian navy warned that oil from the spill could reach Ukraine’s Black Sea coast near Odesa and Mykolaiv, but Ukraine’s Environmental Ministry said a day later that it saw no immediate threat.

Cleanup teams have been responding to oil spills along a coastline of almost 500 miles, collecting more than 160,000 tons of contaminated sand and soil as well as 25 tons of “oil-containing liquid,” Russia’s Emergency Situations Ministry said last week.

But the spill risks becoming a “long-term environmental disaster,” according to Greenpeace Ukraine, which criticized the slow Russian response.

Environmentalists say the spill is particularly difficult to clean up because of the tankers’ cargo. Heavy fuel oil, unlike ordinary regular crude oil, does not stay on the surface of the water, but instead sinks to the bottom.

“If it is not promptly removed from the surface, it remains to wait until it is biodegraded by marine microorganisms,” said Natalia Gozak, the office director of Greenpeace Ukraine. “This can take decades.”