French authorities have seized a Russian shadow fleet tanker and taken its Indian captain into custody, per reports.

The tanker, called Grinch, had sailed from the Russian Arctic Port of Murmansk and was in the Mediterranean Sea when it was intercepted.

French President Emmanuel Macron said that the tanker was subjected to international sanctions and was likely sailing under a false flag.

He added that shadow fleet vessels have helped Russia finance its war against Ukraine.

The tanker is moored and being guarded at a port close to Marseille.

The other crew members, all Indians, are onboard, but the 58-year old captain has been taken for investigation.

The authorities want to confirm the validity of the flag used by the tanker. Per media reports, the tanker was flying the Comoros Islands flag.

Macron announced the tanker’s seizure on Thursday, adding that France is determined to uphold international law and ensure the enforcement of sanctions.

Several Western countries imposed sanctions on Russian energy companies after Moscow invaded Ukraine in 2022.

At the beginning of January, British forces aided a U.S.-led mission to confiscate another Russian tanker in the Atlantic that the latter said had evaded sanctions by loading oil for Russia and Venezuela.

In October, France had intercepted another sanctioned tanker called the Boracay, though it was freed after some days.

Shadow vessels are becoming quite common, with Russia, Iran and Venezuela using them to avoid sanctions placed on them by the West.

S&P Global estimates that one in five oil tankers is used to smuggle oil from sanctioned countries.