PARIS — The French Navy on Thursday boarded a vessel off the Mediterranean coast it suspects of being part of Russia’s embargo-defying shadow fleet.

“The French Navy boarded an oil tanker coming from Russia, subject to international sanctions and suspected of flying a false flag,” President Emmanuel Macron wrote on X.

Last October French forces arrested two crew members on a tanker suspected of belonging to the shadow fleet off Europe’s Atlantic coast.

Hundreds of Russian ships have been cruising international waters since 2022, in violation of international sanctions, to sell oil to fund the country’s war against Ukraine or to transport military equipment. They have typically flown misleading flags and had their transponders turned off to avoid detection. More than 600 of them are currently under an EU ban.

The interdicted vessel, the Grinch, came from the Port of Murmansk, in northwest Russia, local maritime authorities said in a statement. It was boarded in a joint operation with the U.K. near the Strait of Gibraltar in the Western Mediterranean.

“The operation was conducted on the high seas in the Mediterranean, with the support of several of our allies. It was carried out in strict compliance with the United Nations Convention on the Law of the Sea,” Macron wrote, adding that a judicial investigation has begun.