France is braced for another day of public sector strikes and protests against unpopular pension reforms which are expected to be put before the Senate for a final vote later this week.

Trade unions riding a wave of voter support are pushing to force President Nicolas Sarkozy, who faces an election in 18 months, to retreat on plans to lift the retirement age to 62 from 60. So far the government has stood firm even in the face of a fuel shortage caused by striking refinery workers.

France's government sent police overnight to unblock three major fuel depots which had been barricaded by protesters according to Interior Minister Brice Hortefeux.

"During the night, we unblocked three major fuel depots: La Rochelle, Donge and Le Mans," the minister said. Unblocking has already made possible the distribution of millions of litres of fuel, he added.

At least one million people have been demonstrating across France, a sign of the most persistent challenge to economic reforms being enacted across Europe.

Sporadic outbreaks of violence flared on the fringes of some marches, notably in the southeastern city of Lyon, raising concerns for the authorities that small groups of agitators were trying to hijack the predominantly peaceful protests.