Industrial action over labour law reforms is gripping France nationwide, with oil refineries, nuclear power stations and transport hubs affected.
Motorways and bridges were blocked and flights delayed, and 16 arrests were made as a result of clashes in Paris.
Prime Minister Manuel Valls insists the reforms will not be withdrawn but has suggested they could be "modified".
The action, building over three months, comes two weeks before France hosts the Euro 2016 football championships.
A state of emergency imposed after November's deadly attack by militants from the co-called Islamic State group in Paris remains in place.
The CGT union is leading the action, supported by six other unions including Force Ouvriere and Unef, whereas the more moderate CFDT union backs the labour reforms.