The controversy over France’s €1.2 billion deal to build two Mistral warships for Russia appeared to have taken a new twist this week, with reports that Russian sailors had been barred from boarding one of the helicopter carriers at a French port.

A team of around 550 Russian sailors have been in Saint-Nazaire, western France, for several months to receive training on board the Mistral ship.

However several reports in France this week said the sailors have been refused access to the ship.

Regional French newspaper Ouest-France claimed in an exclusive that “several sources” confirmed that Russian sailors were denied the right to board the ship, which is ready to take to the seas.

The decision was apparently made by French authorities, but no specific reason was given, Ouest France reported.

When contacted by The Local on Tuesday both the Ministry of Defence in Paris and French shipbuilder DCNS refused to comment on the story, saying they would neither confirm nor deny whether it was true.

The reports come as France continues to anger Moscow by delaying the delivery date for the first ship, insisting that with fighting ongoing in eastern Ukraine, the “conditions were not in place” for delivery.

France has been under pressure from both the EU and Nato countries, including the US, not to deliver the ships to Russia given the ongoing crisis in Ukraine.

But Paris stands to lose billions of euros in fines and lost revenue if the ships are not handed over.

On Friday, reports said Moscow had handed Paris a deadline for the delivery of the warship and warned of "serious consequences" if it was not met.