Interior Minister Christophe Castaner said on the eve of the strike he expected almost 250 demonstrations nationwide, some of which he said could turn violent.
“We know there will be lots of people in these protests and we know the risks. I have requested that systematically when there is rioting or violence we make arrests immediately,” he said.
On Paris’s famous Champs-Élysées boulevard, riot police began searching pedestrians’ bags before dawn, and shops on a planned protest route have been ordered to close.
How bad is the transport chaos?
Transport networks ground to a near-halt in some areas on Thursday morning.
Some 90% of high-speed TGV and intercity trains have been cancelled, with buses also affected. In Paris, just five of the city’s 16 metro lines are running.
The early rush hour saw deserted stations as commuters shared car rides, took to their bikes or worked from home.
“Public transport will be very difficult today, as it will tomorrow and probably this weekend too,” junior transport minister Jean-Baptiste Djebbari told French station RTL radio.
Train operators Eurostar and Thalys, which run international services, have cancelled at least half their services linking Paris with London and Brussels. Eurostar will operate a reduced timetable until 10 December.
Air travel has been badly affected, with hundreds of flights cancelled. Air France said it would cancel 30% of internal flights and 30% of short-haul international flights, amid walk-outs by air traffic controllers.
Low-cost carrier EasyJet has cancelled 223 domestic and short-haul international flights, and warned passengers to expect delays.
Who else is walking out?
Nurses and hospital staff, lawyers and police officers, refuse collectors, energy staff and postal workers are among others participating in industrial action.
France’s health minister said it was not yet clear how badly hospitals would be affected, but preparations had been made to deal with the strike.
Parents with children of primary school age will also be affected.