MARSEILLE, France June 29 - A French prosecutor ordered on Monday the immobilisation of an oil tanker suspected of being part of the "shadow fleet" Russia uses to ship oil and gas and to skirt Western sanctions.

• The Marseille prosecutor ordered on Sunday the release of the ship's captain who was held in police custody for two days.

• French authorities suspected the ship was sailing under a false flag. It was intercepted off Sicily on June 23, the prosecutor's office said.

• "This new action against the shadow fleet, conducted days after a similar operation by Britain, shows Europeans' determination," Macron said in a post on Instagram last week.

• The oil tanker was sailing from Primorsk in Russia and sailed under a Cameroonian flag.

• The ship is anchored in the Guld of Fos-sur-Mer, off Marseille. A total of 25 crew, including the captain, were on board.

• France has intercepted at least five tankers it says are part of Russia's shadow fleet, old vessels that Russia has relied on to ship oil and gas and to skirt Western sanctions.

• Moscow has called such actions illegal. REUTERS

French prosecutor blocks suspected 'shadow fleet' tanker, releases captain