French workers in several sectors were to vote on Wednesday on whether to strike for a second day after more than a million people marched in the biggest protest yet against pensions reform.
The SNCF national rail company, which ran just one in three trains on Tuesday, said services would likely be as badly disrupted on Wednesday, indicating that workers were expected to renew their strike.
Strikers in the RATP Paris transport network had already voted on Tuesday to renew their action.
"This is not a last stand," said the president of the CFTC union, Jacques Voisin after Tuesday's marches.
"The movement is taking things up a notch."
The nationwide protests were the biggest since the anti-reform battle began earlier this year, unions and police said, estimating the number of demonstrators at 3.5 million and 1.23 million respectively.
That made the street protests the biggest in strike-prone France since 1995, when a month of stoppages crippled the country and forced the right-wing government at the time to drop its own pensions reform.
The strike and marches were against President Nicolas Sarkozy's pensions reform, key elements of which had already passed into law just a day earlier.
And in what some commentators saw as a significant development, students and school pupils joined the movement for the first time.
"Sarko, you're screwed, the young are on the streets," chanted students as they marched beside trade unionists and their supporters on the fourth major nationwide demonstration against pension reform in just over a month.
Travellers faced major delays, with up to half the flights to and from Paris Orly airport and one in three at the capital's Charles de Gaulle-Roissy and the smaller Paris Beauvais cancelled.
Staff also walked out at the Eiffel Tower, forcing the closure of one of France's top tourist draws.
Students at around 400 high schools across the country joined in, the education ministry said. Some barricaded the entrances to their schools with plastic bins.
And operations at 11 of France's 12 mainland oil refineries were disrupted as petrol and dock workers continued their own two-week-old strike against reforms in their sector.
That action has left 56 tankers stuck off the Mediterranean port of Marseille.
The pension reforms, which would raise the retirement age from 60 to 62, are the cornerstone of the right-wing leader's reform agenda as he eyes re-election in 2012. He says they are needed to slash France's budget deficit.
Unions and opposition politicians say the plan puts an unfair burden on workers.
They have proposed balancing the books by, among other things, taxing bonuses and stock options and abolishing a cap on high-earners' personal taxes.
But as a huge crowd of protestors snaked its way noisily though the streets of Paris near the national assembly, Prime Minister Francois Fillon defended the pension plans during a rowdy parliamentary session.
"We are determined to carry through this reform," he said.
Opposition Socialist leader Martine Aubry accused him of overseeing a measure that "symbolises all the injustices and inequalities that characterise his policies and which the French find intolerable."
A CSA opinion poll said 69 percent of French people backed the strike, with 61 percent in favour of more open-ended industrial action.
"I do not think we have lost the battle of opinion," the architect of the reform, Labour Minister Eric Woerth, said on television on Tuesday evening.
The reform bill is edging closer to becoming law as the Senate votes on it article by article. Its deliberations are to last until Friday and the government hopes for the reform to be approved by the end of the month.
"Bringing the country to a halt has never been an aim in itself," said Bernard Thibault, leader of the CGT union, on television on Tuesday evening.
"But that could become a consequence of the government's intransigence."