PARIS, France (AFP) — France and its allies have detained a sanctioned Russian oil tanker in the Atlantic over the weekend, President Emmanuel Macron said on Monday.

The Tagor was detained on Sunday morning in international waters with the help of Britain and other partners, he said in a social media post.

“It is unacceptable for ships to circumvent international sanctions, violate the law of the sea, and fund the war that Russia has been waging against Ukraine for more than four years,” he said.

The Kremlin on Monday slammed the seizure of the tanker as “illegal,” comparing the move to “piracy” after Paris said the vessel was violating sanctions.

“We consider these acts as illegal, they border on international piracy,” Kremlin spokesperson Dmitry Peskov said, adding that “Russia is taking measures to ensure the safety of its cargo.”

The ship’s captain is also refusing to comply with French orders, according to prosecutors.

Since September, France has boarded three other ships believed to belong to Russia’s “shadow fleet.” The ships were allowed to sail after their owners paid fines.

The “shadow fleet” vessels frequently change the flags they fly, a practice known as flag-hopping, or use invalid registrations in an attempt to escape tracking.

Several Western countries have imposed sanctions on hundreds of vessels in Russia’s “shadow fleet” over its 2022 invasion of Ukraine.

Nearly 600 vessels suspected of being part of Russia’s “shadow fleet” are subject to European Union sanctions.