A mass strike against the French government's plan to raise the retirement age disrupted transport and shut down schools, with unions saying two million protestors took to the streets.
Postal workers, gas, electricity and factory workers joined in the movement across the private and public sectors which all but shut down several radio stations, newspapers and theatres.
Bernard Thibault, head of France's biggest union the CGT, estimated countrywide turnout at 1.9 million people, speaking at the start of a huge protest march in Paris.
Police put the turnout lower at 800,000, across some 200 protests including in Lyon, Marseille and Toulouse where strikers marched to the sound of firecrackers and African-style "vuvuzela" horns.
"Hundreds of thousands of voices have spoken out against pushing back the retirement age," said the CGT, accusing the government of "making the workers foot the bill for a crisis they didn't cause."
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"We are headed for a larger-scale conflict if the government persists in this direction," the union warned in a statement.
The government last week unveiled proposals to raise the retirement age from 60 to 62 by 2018, increasing the number of working years required for a state pension, as part of efforts to cut France's big budget deficit.
Nearly one in five civil servants and school staff stayed away from work in protest at the plans which unions says place an unfair burden on workers, forcing schools to close.
Commuters faced disruption across France, with transport authorities saying about one in two mainline trains were running in and out of Paris.
Strike action caused flight cancellations from Paris's main international hubs Charles de Gaulle and Orly.
Performances were cancelled at the Comedie Francaise national theatre and both national Opera houses, while striking print workers prompted daily newspapers such as Le Monde and Liberation to scrap their Friday editions.
Mass protests have forced French governments to back down on social reforms in the past, but the government says it will not bend on raising the retirement age.
Junior jobs minister Laurent Wauquiez said on Thursday it was "normal" to see demonstrators expressing their worries but insisted the government would "try to stay the course with a reform that is a fair reform".
Labour Minister Eric Woerth acknowledged the turnout was "quite strong", but said the protests "will not alter the government's resolve to safeguard our pension system, and in particular to do so by raising the legal age".
However Woerth has already indicated that there is room for negotiation on issues such as allowances for workers with particularly tough jobs.
The pensions reform bill goes before cabinet next month and parliament is to vote on the legislation in September.
A poll by Ifop published this week by the pro-government newspaper Le Figaro said 58 per cent of French people found the planned reform acceptable, though a survey by pollster CSA said 68 per cent sympathised with the protests.
Demonstrators criticised President Nicolas Sarkozy for scheduling a meeting Thursday with French footballer Thierry Henry to discuss France's humiliating exit from the World Cup, which dominated the news on Thursday.
"Sarkozy doesn't care anyway," said Marcel Bonnet, 63, protesting in Lyon. "While we're here, he's meeting footballers."
