France's detention of a tanker suspected of operating for Russia's "shadow fleet" is part of a new European strategy to block revenue funding Moscow's war effort in Ukraine, President Emmanuel Macron said on Thursday.

Macron added that it was yet to be determined whether the vessel had been involved in drone incursions in Denmark last week, which shut Danish airports close to the route that the ship was sailing on from the Baltic to the North Sea.

French Navy commandos raided the Boracay on Saturday off western France. The vessel was already under EU and British sanctions for suspected participation in Russian oil exports.