Refinery workers, airport staff, train drivers, teachers, postal workers and guards who supply cash machines went on strike and students set off rowdy protests in a day of action against plans to raise the minimum retirement age to 62 from 60.

At least a million protesters demonstrated in cities across France in the biggest and most persistent challenge to economic reforms anywhere in Europe, where governments are struggling to curb budget deficits and reduce debt mountains.

The protests have blown up into the biggest test yet for Sarkozy, whose popularity ratings are dismal 18 months before a presidential election which polls show the left would win as things stand today.

The unrest has put him under an uncomfortable spotlight as France prepares to take over the G20 presidency in mid-November.

Speaking in the seaside town of Deauville where he met the leaders of Russia and Germany, Sarkozy appealed for restraint as hooded protesters in the southern city of Lyon torched cars and looted shops after using cafe chairs to smash windows.

He said pension reform had been put off too long in France, where unions have a history of crushing such initiatives.

The CGT union put turnout at 3.5 million, on a par with its record-high estimate for protests earlier in the month. The government said 1.1 million people had turned out.