PARIS — Maintaining a tough line, President Nicolas Sarkozy warned on Thursday that “troublemakers” using violence in the protests against his proposed pension changes would be pursued and punished “with no weakness” on the part of the authorities.
The president spoke at a meeting with rural officials southwest of Paris as strikers blocked traffic in several cities and other protesters vowed to continue weeks of efforts to thwart the retirement changes on which Mr. Sarkozy appears to have staked his political future.
Mr. Sarkozy said strikers and demonstrators blocking fuel depots did not have the right to “take hostage people who have nothing to do with it.” He was referring to 10 straight days of strikes at refineries and blockades of fuel depots that have left motorists struggling to find fuel.
While the authorities said Thursday that there had been a “slow improvement” in fuel supplies with only 14 out of more than 200 depots still blockaded, service station operators said about half of the country’s 13,000 gas stations were experiencing supply problems.
The crisis shows little immediate sign of ending and a final parliamentary vote on Mr. Sarkozy’s plan to raise the minimum retirement age to 62 from 60 seemed unlikely until the middle of next week.
Referring to several days of clashes between the police and protesters in Lyon, which continued on Thursday, Mr. Sarkozy said the “troublemakers will not have the last word in a democracy, a republic.”
“It is not acceptable,” he said. “They will be stopped, tracked down and punished, in Lyon and anywhere else, with no weakness. Because in our democracy, there are many ways to express yourself. But violence is the most cowardly, the most gratuitous, and that is not acceptable.”
Earlier on Thursday, strikers blocked the access road to the airport in the southern port of Marseille for several hours and held up traffic near the cities of Rouen, Toulon, Le Havre and elsewhere, news reports said. The actions came a day before the start of midterm school vacations whose impact on the strikes and protests was unclear.
Education authorities said 312 of the country’s 4,300 high schools had been closed or disrupted on Thursday because of protests by students, some of whom planned a march in Paris.
On Wednesday, Mr. Sarkozy ordered the police to reopen all the blocked fuel depots and warned of economic dislocations from the continued protests.
“If this disorder is not ended quickly, the attempt to paralyze the country could have consequences for jobs by disrupting the normal functioning of the economy,” Mr. Sarkozy told his cabinet. Unions are considering another day of demonstrations on Tuesday. But some union leaders acknowledged that time was running against them, and some quietly acknowledged concern that the largest and most radical French union might be pushing the protests too far.
That union, the C.G.T., was once allied with the Communist Party. It is the largest union among refinery, port, gas and power workers, some of whom are more radical than the union’s leadership.
François Chérèque, head of the second largest French union, the C.F.D.T., called on demonstrators to remain calm and not to give in to provocations, while the white-collar union, the C.F.E.-C.G.C., announced that Tuesday’s demonstration would be its last. Its president, Bernard Van Craeynest, said that in the face of excesses, “it will be necessary without doubt to pause to reorient the actions” of the unions.
He added, “We find ourselves in a situation where the movement is going in all directions.”
But with the more radical union members deployed at choke points for fuel and gasoline supplies, and with more young people protesting, the tone of the demonstrations became more aggressive, making it easier for Mr. Sarkozy to try to shift the public’s focus to the restoration of order.
The interior minister, Brice Hortefeux, warned rioters that “the right to protest is not the right to break things, the right to set things on fire, the right to assault, the right to pillage.” He added: “We will use all means necessary to get these delinquents.”
Drivers hunted for gasoline, some of them calling the police to ask what stations still had supplies. Often refills were limited. France’s 11 active refineries remain on strike, though officials ordered employees at one to return to work. France has been importing large amounts of electricity, and prices have been rising.
The political scientist Jacques Capdevielle noted with surprise that while only 4 percent of French workers were unionized, credible polls showed that a majority of the French supported the strike.
Jean-François Copé, parliamentary leader of Mr. Sarkozy’s party, said Wednesday that this was “the week of truth” on the pension overhaul and emphasized “the cohesion of the majority and the government” on the change, saying, “There is no other solution to save our pension system.”
He then criticized the opposition Socialist Party for promoting the demonstrations without a viable legislative alternative and for calling students into the streets. He said he was appalled that “a handful of people have taken the economy of our country hostage by blocking the fuel depots.”
Prime Minister François Fillon said in the National Assembly that the protests would fade once the law was in place. He cited other pension changes, in 1993, 2003 and 2007, that had also prompted protests, but “progressively became the law of the republic, accepted by a very large majority.”
He added that “social confrontation is part of our democracy, but social consensus is, as well.” He did not mention 1995, when widespread protests caused the government to drop a pension change.