MOSCOW, Jan 10, 2025 (BSS/AFP) - Fresh oil started pouring from a stricken Russian tanker in the Black Sea on Friday, said officials in Moscow, as Ukraine warned of "terrible environmental consequences" from the spill.

Heavy fuel oil has been washing up on hundreds of kilometres of beaches along Russia's southern coast and on the annexed peninsula of Crimea since two ageing Russian tankers were caught in a storm in the Kerch strait on December 15.

One of the vessels, Volgoneft-212, sank, and another, Volgoneft-239, ran aground and broke apart.

"While inspecting the stern part of the Volgoneft-239 this morning, specialists discovered an oil slick of about 2,800 square metres on the shore," Russia's transport ministry said on social media.

The vessel is beached near the port of Taman in Russia's southern Krasnodar region, across the Kerch Strait from Crimea, which Russia annexed from Ukraine in 2014.

Images published by the Russian cleanup task force showed thick black fuel running from the stranded vessel along the beach.

Russia said earlier in January that some 2,400 tonnes of mazut had been spilt by the two tankers, which were loaded with 9,200 tonnes between them.

Mazut is a heavy fuel oil that is difficult to clean up as it does not float on the surface.

- 'International irresponsibility' –

Russian President Vladimir Putin has called it one of the "most serious environmental challenges" Russia has faced in recent years. Hundreds of birds and dozens of marine animals have died.

Ukraine on Friday slammed Russia for failing to handle the spillage.

Foreign ministry spokesman Georgiy Tykhy accused Russia of "international irresponsibility".

By trying to "conceal the terrible environmental consequences" Moscow had left the entire Black Sea region vulnerable to the fallout, he said.

More than 147,000 tonnes of contaminated sand and soil have been removed from beaches in southern Russia and Crimea so far.

Oil slicks have been detected as far as away as the Crimean city of Sevastopol, around 250 kilometres (155 miles) from the site of the incident.

Maya Meshkarudnik, a volunteer trying to save birds covered in oil told AFP the "smell of fuel oil" was hanging in the air at her country house, 15 kilometres from Anapa, a resort town heavily affected by the spillage.

Almost four weeks after the incident, Putin on Thursday criticised local officials' clean-up operation -- which has relied on thousands of volunteers shovelling sand and soil off beaches.