France is being hit by serious disruption as unions lead strike action at oil refineries, nuclear power stations, ports and transport hubs.
Motorways, bridges and tunnels have been blockaded, and flights and rail services affected.
Nuclear power production has slowed, and fuel remains in short supply.
PM Manuel Valls has again insisted that labour reforms at the heart of the dispute would not be withdrawn, but suggested they could be “modified”.
The French government is under increasing pressure to give ground as the country prepares to host the Euro 2016 championships in two weeks’ time, correspondents say.
The unions have called for rallies in most major cities.
Hundreds of workers marched into the port city of Le Havre, in Normandy, having blocked off the nearby Bridge of Normandy.