France's navy has intercepted a sanctioned tanker linked to the Russian oil trade in the Atlantic Ocean and ordered the vessel to head for the French mainland, in a move Russia said was illegal and bordered on "international piracy".

French President Emmanuel Macron on Monday posted a video on X showing commandos rappelling from helicopters onto the Tagor, during an operation that occurred the previous day in international waters 740km west of Brittany.

The tanker, which had sailed from Russia's Arctic port of Murmansk, was suspected of flying under a false flag, and was intercepted with support from Britain, Macron said. According to the vessel tracker MarineTraffic, the 252-metre-long tanker was sailing under the flag of Madagascar.

France's Maritime prefecture, the state authority for maritime security, said the boarding team's inspection of the vessel's papers had "confirmed suspicions regarding the irregularity of the flag flown."

To try to skirt Western sanctions, Russia has relied on old vessels, known as the shadow fleet, to ship its oil and gas. France and Britain have both vowed to obstruct such vessels as part of a European strategy to combat the oil revenues that help fund Russia's war efforts in Ukraine.

"It is unacceptable for ships to circumvent international sanctions, violate the law of the sea, and finance the war that Russia has been waging against Ukraine for more than four years," Macron wrote on X.

On Monday, the Tagor was steaming under naval escort towards an anchorage off northwestern France, according to the Maritime prefecture.

The Tagor is the fourth sanctioned tanker the French have intercepted.

The European Union has imposed 19 packages of sanctions against Russia, but Moscow has adapted to most measures and continues to sell millions of barrels of oil to countries such as India and China, typically at discounted prices.

Western sanctions and a small number of interceptions have had little obvious impact on the "shadow fleet" at a time oil prices pushed higher by the Iran war offer tankers a big incentive. Instead it is the Ukrainian strikes on Russian oil facilities that are stopping Moscow from capitalising on the spike in global fuel prices.

Moscow's reaction to the seizure will be closely watched.

Kremlin spokesman Dmitry Peskov told journalists on Monday Russia would take measures to ensure the safety of shipping cargo in response to the incident. (Reuters)


Edited by Edmond Fong