An oil tanker was set ablaze off the Russian resort city of Sochi on Tuesday evening after being struck by naval drones, Russian officials said, sending a towering column of black smoke over the Black Sea coast.

Russia's transport ministry said the Liberian-flagged Aframax Rio had been attacked by 'unmanned boats' and that 'crude oil is burning openly in the waters of the Black Sea'.

All 23 crew members, who the ministry said were Indian citizens, were rescued. Preliminary information indicated there were no casualties.

Fire too fierce to fight

Images and videos shared widely on social media showed bright orange flames on the water and thick smoke drifting across parts of the city, which has a population of almost 500,000 and hosted the 2014 Winter Olympics.

The ministry said firefighters could not yet tackle the blaze because of its intensity and would attempt to extinguish it once it had died down. Authorities in the neighbouring settlement of Sirius had earlier reported the fire on board, and beaches there were closed to the public. Sochi's mayor said access to the coast was being restricted.

Russia did not immediately say who it held responsible. International news agencies reported that Ukraine was behind the strike; Kyiv did not immediately comment in detail.

A war at sea

Both countries have repeatedly targeted commercial shipping in the Black Sea since Russia's full-scale invasion in 2022. Russia has in recent days struck grain vessels carrying Ukrainian exports near the coast of Romania, an EU member state.

President Volodymyr Zelensky separately blamed Russia for an attack on Bulgarian vessels in the Black Sea, and an investigation has been launched. Moscow has not commented on that accusation.

Ukraine describes its attacks on Russian energy infrastructure as legitimate retaliation for Russia's sustained bombardment of Ukrainian towns and cities, and as an effort to cut the oil revenues that fund Moscow's war effort. Russia condemns them as terrorism and says it is responding to attacks on its own territory.

Same day, deadly strikes in Ukraine

The tanker fire came on the same day as a large Russian missile and drone attack on Ukraine. Zelensky said at least 11 people had been killed and 34 injured, describing it as a 'vile' attack carried out on President Vladimir Putin's birthday.

Russia says its strikes target military and energy facilities. Ukraine says civilians and residential buildings are repeatedly hit.

Russian officials, meanwhile, reported a very large Ukrainian drone attack directed towards Moscow in recent days, part of an escalation that has seen both sides vow to intensify long-range strikes.

Environmental fears

Previous attacks on oil facilities and tankers in southern Russia have caused oil slicks, beach closures and episodes of oily black rain falling on nearby communities. Environmental groups have warned that the cumulative damage to the Black Sea is mounting.

Aframax is also the industry name for a class of medium-sized crude oil tankers, widely used on regional routes such as those serving Russia's Black Sea ports, including Novorossiysk, one of the country's main oil export terminals. The vessel's owner and the destination of its cargo were not immediately disclosed.

Local authorities did not immediately say how much oil the Aframax Rio had been carrying or whether a slick was spreading towards the shore.

Why it matters

Tankers carrying Russian crude are a key part of the oil export trade that underpins Moscow's budget. Attacks on shipping raise insurance costs, deter operators and carry the risk of a wider maritime confrontation involving vessels from countries not party to the war, as the Indian crew of the Aframax Rio demonstrates.

With both governments promising further escalation, the waters off Russia's most famous holiday resort have become one more front line in a conflict now well into its fifth year.