France has started using its fuel reserves to deal with petrol shortages caused by strikes and protests over a bill weakening worker protections.
Unions are targeting the nation's petrol tanks, railways and electricity network this week as they try to push the government to drop the labour reform, devised to make France more globally competitive by extending the work week and making lay-offs easier.
Opponents say it will enrich company bosses and will not create the jobs it promises.
The head of the group overseeing France's petroleum industry, UFIP, said on Wednesday on RMC radio that the government has approved the use of fuel stocks for the past two days.
Francis Duseux said there are about three months of reserves that could be used if needed.
He acknowledged "the situation is tense" but attributed it to panic buying. "Demand is so high that we aren't managing to keep up," he said.
Unions have blocked depots and refineries around France to try to bring road traffic to a halt. Workers at a major oil terminal in the port of Le Havre plan a strike on Thursday to block imports.
Riot police forced striking workers out of a fuel depot early Wednesday in Douchy-les-Mines in northern France that had been blocked for several days, Sud union member Willy Dans said on BFM television.
Meanwhile, train drivers also staged a one-day strike on Wednesday. The SNCF national rail authority said 25% of high-speed TGV trains were cancelled, and a similar number of regional and commuter trains were affected.
And workers at the country's nuclear plants - source of the majority of France's electricity - plan a one-day strike on Thursday. State-run Electricite de France would not comment on the eventual consequences for electricity supplies around the country.
The CGT union, whose hard-left flank is driving the nationwide strikes, is also threatening to block a reactor at a plant in Nogent-sur-Seine, south east of Paris, that was shut for technical reasons and is scheduled to be restarted Wednesday.
President Francois Hollande's government made compromises in the labour bill earlier this year to meet union demands, but refuses to abandon it. Government ministers say they will continue sending police to clear protesters and ensure petrol supplies.