The strikes are seen as a test for the conservative Sarkozy and are being watched elsewhere in Europe, as governments struggle to rein in costs with unpopular austerity measures after the Greek debt crisis scared markets and sapped confidence in the entire 16-nation euro currency.
Protesters brandishing flags, balloons and signs gathered at Paris' Place de la Bastille, the iconic site of the French Revolution and starting point for the French capital's demonstration, which was snaking through the eastern Paris to the Left Bank.
Turnout at the 232 demonstrations nationwide was key to Thursday's showdown between unions and the unpopular Sarkozy. Labor leaders urged people to march in even greater numbers than during the last round of protests, on Sept. 7, which brought at least 1.1 million people into the streets.
It's no surprise, then, that estimates of protesters varied wildly.
In the Mediterranean port city of Marseille, police put turnout at 22,000, while organizers said it was ten-fold higher. Paris police said 65,000 people turned out for the capital's march, compared with 80,000 earlier this month.
Organizers put turnout at the Sept 7. Paris march at 270,000, but haven't yet released an estimate for Thursday's demonstration.
Sarkozy has indicated he is willing to make marginal concessions but remains firm on the central pillar: increasing the retirement age from 60 to 62 and pushing back the age from 65 to 67 for those who want full retirement benefits.
As baby boomers reach retirement age and life expectancy increases in France, the conservative government insists it must raise the retirement age so the money-losing pension system can break even by 2018.
Sarkozy's reform passed a vote in the National Assembly lower house of Parliament but still faces other hurdles — including an upcoming debate in the Senate — before becoming law.
"This is not over yet," said Bernard Thibault, who heads the CGT labor union. "We are getting closer. And the best answer ... is to gather again several million workers who are on strike and take it to the streets." The leftist opposition sees retirement at 60 as a sacred symbol of France's social welfare system. They say Sarkozy's reform won't fix the problem and have also insisted any changes must make more exceptions for certain categories of workers.
"An increasing number of French people understand that the reforms the president is trying to impose will not solve the pensions issue," Martine Aubry, the head of the opposition Socialist party, told journalists at the Paris march. "Pensioners will pay the price for it. And tomorrow, young people will not benefit from government-funded pensions — the only system that is fair and shows solidarity between generations." A poll in the left-leaning Liberation daily suggested that 63 percent of respondents supported the strikers, while just 29 percent of those polled supported the government.
Almost 60 percent opposed the plan to raise retirement age, with 37 percent in favor, according to the poll, conducted by the Viavoice agency on Sept. 16 and 17 with 1,002 respondents.
A demonstrator in the northern city of Lille, 48-year-old teacher Odile Deverne, said she found the pension reform "unfair." "Those who will cope are those who will be able to save some money. The others will retire with nothing but having worked much more than before," she said.
Walkouts disrupted travel and commutes across France, and post offices and even opera houses were hit too.
Traffic was snarled in France's cities, with fewer than half of the Paris Metro's lines working normally, according to the RATP public transit network, and about half of France's long-distance trains canceled, according to the SNCF state-run rail system.
Security was higher than usual at some Metro stations, where soldiers armed with machine guns were on patrol. In recent days, top officials have warned that the risk of a terrorist attack on French soil was at a record high.
The Eurostar undersea train service to London was not expected to be affected and the Thalys train from Belgium was only slightly disrupted, with nine in 10 trains running.
While the French capital's bus lines were running almost normally, commuters on some Metro lines had to queue up just to get on the platforms.
Some commuters opted out of public transit, taking their cars or using Velib, Paris' rent-a-bike network, including Paris commuter Xavier Roth.
"Even the scooters struggle to ride between cars, and walking takes a long time, so for me a bicycle is the ideal compromise," he said.
The main teachers' union said over 50 percent of teachers were expected to strike, though the Education Ministry put the figure at just over 25 percent.
At the SNCF national railway, about 38 percent of employees heeded the call to strike, according to the management. Some SNCF unions have already called for new strikes beyond Thursday.
Even at 62, France would have one of the lowest retirement ages in Europe. Neighboring Germany has decided to bump the retirement age from 65 to 67.
The US Social Security system is also gradually raising its retirement age to 67.
