A nationwide strike against the French government's plan to plug a 20-billion-euro hole in the country's pension system has passed quietly.

The strike called by four unions against the Socialist government's proposed reform had almost no impact on traffic across France's rail, bus and subway systems or other public services. That is a sharp contrast to the sometimes violent protests that erupted the last time a French government attempted to reform its retirement system.

Demonstrations in Paris and 180 other towns and cities were taking place, but with some moderate unions declining to participate, mobilisation withered.

The French plan would gradually extend the number of years employees must pay contributions to claim a full pension, from 41.5 years now to 43 years in 2035.