France moves seized Russian "shadow fleet" tanker to Marseille

"It will be anchored and held at the disposal of the Marseille public prosecutor as part of the investigation into the alleged offence of sailing under a false flag," it added.

The Russian embassy in France on Thursday called the seizure "another case of piracy" and "illegal and unacceptable from the point of view of international law", the TASS news agency reported.

A military source has said its was operating under a Cameroonian flag, despite having been formally struck off Cameroon's registry weeks earlier, meaning it was navigating without nationality and breaching international maritime law.

This enabled France to board and detain it, the source said.

(Reporting by Dominique Vidalon; Editing by Andrew Heavens)