France announced Monday another weekend interdiction of a Russian "shadow fleet" vessel in international waters near its coast. The French Navy boarded and detained a sanctioned oil tanker, President Emmanuel Macron announced Monday, in an operation which had the assistance from the UK Royal Navy and other allies.

This marks the fourth time since September that French commandoes have intercepted a boarded a sanctioned Russian vessel in regional waters.

The vessel, identified as the Tagor, originated from Murmansk, Russia, and was taken by French authorities while it traversed around 400 nautical miles (740 km) west of the tip of Brittany.

"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 4 years," Macron wrote in a post on X.

The apparent legal justification France's navy has relied on for such actions is the practice of "flag-hopping" - which involves a crew repeatedly changing displayed flags, along with often invalid registrations to thwart international tracking monitors.