Workers with the country's most powerful union, the leftist CGT, are blocking six of France's eight oil refineries, some of its fuel depots, and plan to shut down or lower output in at least six of its nuclear power plants in a bid have a new labour law scrapped.
How bad are the blockages?
Up to a third of petrol stations are running on empty while panic-buying has worsened the shortage, forcing the state to delve into its strategic petrol reserves, which could theoretically keep pumps flowing for three months.
Although almost 80 per cent of France's electricity comes from nuclear power, experts say there will be no blackouts if a few of its 58 reactors are shut, and besides staff are under obligation to respect a minimum service.
What do unionists want?
President François Hollande's Socialist Government to scrap the labour bill they see an assault on hard-fought workers' rights.
What does the reform do?
The so-called El Khomri labour law (named after the French labour minister, Mariam El Khomri) is a modest attempt to loosen France's labour market by, among other things, making it slightly easier to make employees redundant in hard economic times.
The aim is to encourage notoriously reticent French employers to take on more workers on permanent contracts, rather than short-term ones, without fear of being stuck with them for life or paying heavy fines at the workers' tribunal.
It also includes provisions for negotiations on, say, working hours, to take place within individual companies rather than across sectors.
The Government believes it will create thousands of jobs but the IMF and the French opposition say the reform doesn't go nearly far enough to significantly reverse record unemployment, now at 10 per cent, and soaring public debt, due to reach 98 per cent of GDP next year.
What do the French think of it?
Three-quarters of the French said they are against the law, a poll this month suggested.
How did they express their opposition?
A million people signed a petition against it in February, then mid-March, hundreds of thousands of French started nightly rallies against the bill in a movement dubbed "Nuit Debout", or Up All Night. Unions staged seven national days of protest, with an eighth planned tonight NZT.
Why has the CGT escalated the standoff?
Its leader, Philippe Martinnez, wants to burnish his credentials as a tough defender of workers' rights among die-hard leftists at a time when the CGT is losing members.
How has the Government reacted to the blockages?
It ignored earlier protests and bypassed a parliamentary vote to push through the bill.
Manuel Valls, the Prime Minister, pledged to stand firm, saying: "The CGT doesn't make the law in France."
Hollande knows if he caves in his small hopes of re-election next year will be totally dashed.
They reportedly hope to win a "war of attrition" against the strikers in the hope the French will grow tired of the blockages. Some 58 per cent of French are against the protests, one poll has suggested.
Is more industrial action planned?
Yes, unions have called a national day of protests tomorrow, plus open-ended national train and metro strikes starting on June 1 and June 3 respectively.
Could the blockages affect the Euro 2016 football tournament in France, which starts on June 10?
Yes. The unions have already made it clear that "workers come before football".
A poll suggested that 56 per cent of French fear the competition will be disrupted, and an even higher number are concerned that this will prove "catastrophic" for France's image abroad.