France says it has seized an oil tanker in the Mediterranean suspected of being part of Russia's sanction-busting shadow fleet.

French President Emmanuel Macron stated that the tanker, named the Grinch, was subject to international sanctions and suspected of flying a false flag.

The French navy, with assistance from allied forces including the UK, boarded the vessel on Thursday between Spain and Morocco. French maritime authorities confirmed that searches revealed irregularities regarding the flag.

Russia's embassy in Paris has noted that it was not informed about the seizure.

Moscow's so-called shadow fleet consists of a network of tankers used to evade Western sanctions on Russian oil by transporting it on older vessels with obscure ownership.

The Grinch was en route from the Arctic port of Murmansk in northern Russia when it was intercepted. Ship tracking websites indicated that it had been flying a Comoros flag.

In a statement on social media, Macron declared: We are determined to uphold international law and to ensure the effective enforcement of sanctions. The activities of the 'shadow fleet' contribute to financing the war of aggression against Ukraine, adding that the vessel had been diverted.

UK Defence Secretary John Healy noted that the UK navy offered tracking and monitoring support, with HMS Dagger observing the tanker through the Straits of Gibraltar.

He remarked: Alongside our allies, we are stepping up our response to shadow vessels to choke off the funds that fuel Putin's illegal invasion of Ukraine. The UK has imposed sanctions against 544 vessels related to the Russian shadow fleet.

Ukrainian President Volodymyr Zelensky applauded the action, stating it was the exactly the kind of resolve needed to ensure that Russian oil no longer finances Russia’s war. He urged nations to capture and sell the oil carried by such tankers.

Many Western nations have enacted sanctions on Russian energy in response to Russia's full-scale invasion of Ukraine in 2022.

Earlier this month, British armed forces assisted a US operation to seize a Russian-flagged tanker in the Atlantic that was allegedly breaking sanctions by transporting oil for Venezuela and Russia.

Moscow condemned this action, asserting that no country has the right to use force against vessels registered under other nations' jurisdictions.

Last October, France seized another tanker, the Boracay, off its coast but released it shortly after.

Shadow fleets are becoming increasingly common, with countries like Venezuela, Iran, and Russia accused of using them to bypass sanctions on oil. Financial intelligence firm S&P Global estimates that one in five oil tankers globally is involved in smuggling oil from sanctioned countries.