French naval forces intercepted a Russia-linked oil tanker in the Mediterranean Sea on Thursday, as part of a mission targeting sanctioned Russian shadow fleet, authorities said.

"This operation was carried out... with the support of several of our allies. It was conducted in full ‌compliance with the United Nations Convention on the Law ‍of the Sea," French President Emmanuel Macron said on the social media platform X.

The interception was carried out on high seas in the Western Mediterranean, between the southern coast of Spain and the northern coast of Morocco, the French maritime police said in a separate statement.

Authorities said the ship, the Grinch, is suspected of operating with a false flag. The French navy is escorting it to an anchorage for more checks, the statement said. The tanker departed from the city of Murmansk in northwestern Russia, it added.

The EU 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.

Oil revenue is a key part of Russia's economy, allowing President Vladimir Putin to pour money into the war effort against Ukraine without worsening inflation for everyday people and avoiding a currency collapse.

France and other countries have vowed to crack down on the sanction-busting shadow fleet of oil tankers which experts estimate numbers over 400 ships. They are also trying to secure deals with flag-carrying countries to make it easier to board the vessels.

Russia is using what is described as a "shadow fleet" to evade sanctions over its war on Ukraine. The fleet is a compilation of aging vessels and tankers owned by nontransparent entities with addresses in non-sanctioning countries, and sailing under flags from such countries.

"We are determined to uphold international law and to ensure the effective enforcement of sanctions," Macron said in the post about the interception, with a photo showing a French helicopter hovering over a ship.

"The activities of the 'shadow fleet' contribute to financing the war of aggression against Ukraine," Macron added.

Ukrainian President Volodymyr Zelenskyy welcomed ‍the operation, saying such action was "exactly the kind of resolve ⁠needed."

"Vessels must ‌be apprehended. And wouldn't ​it be fair ‍to confiscate and ‍sell ​the ‍oil carried ⁠by ‍these tankers?" Zelenskyy wrote on X.

The case was referred to the prosecutor of Marseille, who handles ‍matters ​related to ‍maritime law. The prosecutor ordered the ship to be ⁠diverted for further investigation.

Moscow said France ‍had not notified Russia about the interception, TASS news agency reported.

The Russian consulate in Marseille is trying to find out whether Russian citizens are among the crew members, TASS reported, citing the Russian embassy in France.

The French mission was conducted together with the U.K, which gathered and shared intelligence that enabled the ship to be intercepted, according to French military officials who spoke to The Associated Press (AP) on condition of anonymity to discuss details of the operation.

The ship was operating under a false flag from the Comoros islands, which are off east Africa, and its crew is Indian, the officials said.

Last September, French naval forces boarded another oil tanker off the French Atlantic coast that Macron also linked to the shadow fleet.

That tanker traveled from the Russian oil terminal in Primorsk near Saint Petersburg. Known as "Pushpa” or "Boracay" – its name was changed several times – the ship was sailing under the flag of Benin.

Putin denounced that interception as an act of piracy and alleged that Macron initiated the move to deflect attention from French domestic problems.

The tanker's captain will go on trial in February over the crew's alleged refusal to cooperate, according to French judicial authorities.