Environmental groups say the damage caused by oil leaking from two damaged Russian tankers in the Kerch Strait could have a devastating impact on marine life in the area.
Fears of environmental disaster following oil spill from Russian ships
Footage posted on social media showed birds along the shoreline covered in mazut on Monday, after 3,700 tonnes of the heavy, low-quality oil product spilled into the strait
The two ageing ships were badly damaged in stormy weather in the Black Sea over the weekend.
They were transporting roughly 9,200 tonnes of mazut. Footage from the scene also showed a black liquid rising among the waves.
The Kerch Strait separates Russia from Crimea, the Ukrainian peninsula illegally annexed by Moscow in 2014.
The leader of Russia’s nearby Krasnodar region, Governor Veniamin Kondratev, said the oil spill was "removable".
"We can say with confidence that there will be no threat to the 2025 resort season," he added.
An emergency rescue operation was launched Sunday after the first tanker ran aground and had its bow torn away in storm conditions. Officials said one sailor in the 13-man crew died.
A second tanker was also left damaged and adrift with 14 crewmembers on board. It later ran aground 80 meters from shore, close to the port of Taman in Russia’s Krasnodar region.
The sailors on that ship were all rescued.
Ukraine's environmental ministry said the leak could have "catastrophic consequences for the marine ecosystem".
It is important area for migrating dolphins and other sea mammals.
Kyiv accused Russia of failing to comply with maritime safety rules.
The Kerch Strait is also an important global shipping route, providing passage from the Sea of Azov to the Black Sea.
It has been a key point of conflict between Russia and Ukraine after Moscow annexed the peninsula from Ukraine.