They are protesting plans to change special pensions deals which allow certain workers to retire as young as 50 on favorable terms.

The strike has been prolonged to overlap with Sarkozy's latest industrial headache: an unrelated 24-hour stoppage by public sector workers, including teachers, hospital staff and postal workers. State employees from defense ministry secretaries to weather office staff will stop work to protest low salaries and public sector job cuts.

The president is said to be standing firm on his "modernizing" agenda, in the face of a "black November" of protests against his reforms.