Truck drivers continued to blockade strategic parts of the road network on Thursday and train services were reduced by more than 50 percent by a second day of strikes.

Trading sources estimated that at least 50 percent of runs at the five Total refineries, amounting to more than 400,000 bpd of crude, have been cut.

"They cannot go lower or they'll have to shut down," CGT delegate Thierry Defrense told Reuters, adding that the Grandpuits and Donges refineries are at risk of shutting down fully on Friday.

"It is not just refineries, it's the whole country," one trader said. "They can't import or export products and will continue to draw on inland inventory."

Benchmark European diesel refining margins hit 2016 highs on Wednesday, partly on the back of the strikes.

"Ultimately, if there's no crude coming into a port, as in the case with Fos, etc, that impacts not just Fos but a whole load of other refineries that depend on that route for supply," another trading source said.

A Total spokesman said: "Our refineries are functioning normally at the moment although, given the context, we are experiencing some expedition blockages at certain points."

He added that some petrol stations in some regions had run out of fuel.

An Exxon Mobil spokeswoman said that operations at its two refineries in France are continuing as normal.

PetroIneos could not be immediately reached for comment, but the company's Lavera refinery in southern France is thought to be in a planned maintenace shutdown.

(Reporting by Bate Felix in Paris, Ahmad Ghaddar in London and Libby George in New York; Editing by Keith Weir and David Goodman)

Stocks treated in this article : Total, Exxon Mobil Corporation