PARIS (AP) — French President Nicolas Sarkozy is pledging to crack down on "troublemakers" attacking police at protests against a proposed higher retirement age.

He also says blockages of oil refineries that have sparked gas shortages "cannot exist in a democracy" where "there are people who want to work."

He insists it's his "duty" to pass pension reform, despite nationwide strikes and violent protests.

Sarkozy says demographics and people's increasing life expectancy have made raising the retirement age from 60 to 62 a necessity and stressed that other European nations have already made similar changes.

Sarkozy was speaking Tuesday at a press conference in the French city of Deauville with the leaders of Russia and Germany.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

PARIS (AP) — Some airliners steered clear of France and police clashed with stone-throwing youths Tuesday as a new round of nationwide strikes and protests over a bill raising the retirement age to 62 kicked off.

Workers in sectors across the French economy joined in one-day strikes Tuesday after a week of disruptions by protesting oil refinery workers, students and employees of the SNCF national railway operator. More than 200 protests are planned around the country Tuesday.

It was the sixth national day of demonstrations over the planned pension reform since early September. Union leaders have vowed to keep up the pressure until the government scraps the unpopular plan, saying retirement at 60 is a fundamental social right that past generations fought hard to achieve.

President Nicolas Sarkozy says it must go through to save France's generous but money-losing pension system. The protests in France come as countries across Europe are cutting spending and raising taxes to bring down record deficits and debts from the worst recession in 70 years.

The Paris airport authority warned on its website and in signs at the airports: "Strike on Oct. 19. Serious difficulties expected in access to airports and air traffic." France's DGAC civil aviation authority said up to half of flights Tuesday out of Paris' Orly airport would be scrapped, and 30 percent of flights out of other French airports, including the country's largest, Charles de Gaulle, serving Paris, would be canceled.

Most cancellations were expected on short- and medium-haul domestic and inter-European flights. The walkout by air traffic controllers was expected to last one day, with flights expected to return to normal on Wednesday.

Strikes by oil refinery workers have been ongoing, sparking fuel shortages that forced at least 1,000 gas stations to be shuttered. Others saw large crowds. At an Esso station on the southeast edge of Paris on Tuesday morning, the line snaked along a city block and some drivers stood with canisters to stock gasoline in case of shortages.

Truckers have joined the protest, running so-called "escargot" operations in which they drive at a snail's pace on highways. On Tuesday, about 20 truckers blocked an oil depot in Nanterre west of Paris operated by oil giant Total, turning away fellow truckers coming to fill up with gasoline. Police stood by but did not intervene.

"If they (the government) continue, we won't have any choice (but to continue)," said Jorge Goncalves, a trucker with the CFDT union blocking the Nanterre depot. "Today the government is stubborn. And how do you deal with stubborn people? You don't let go,"

Students entered the fray last week, blockading high schools around the country and staging protests that have occasionally degenerated into clashes with police.

Across the country, 379 high schools were blocked or disrupted Tuesday to varying degrees — the highest figure so far in the student movement against the retirement reform, according to the Education Ministry.

At a high school in the Paris suburb of Nanterre closed because of earlier violence, a few hundred youths and nearly as many police gathered Tuesday morning.

The teens started throwing stones from a bridge, and police responded with tear gas and barricaded the area. It was not immediately clear if there were injuries or arrests. Nanterre has often seen student protests in past years.

In the Nanterre clashes, youths knocked an Associated Press photographer off his motorbike and kicked and punched him as they rampaged down a street adjacent to the school.

Justice Minister Michele Alliot-Marie pledged on Europe-1 radio Tuesday to stay firm against "troublemakers" on the margins of the protest movement.

The head of the UNEF student union, Jean-Baptiste Prevost, countered that students "have no other solution but to continue."

"Every time the government is firm, there are more people in the street," he told i-tele news channel, predicting a large turnout for Tuesday's street marches.With disruptions on the national railway entering their eighth consecutive day Tuesday, many commuters' patience was beginning to wear thin. Only about one in two trains were running on some of the Paris Metro lines, and commuters had to elbow their way onto packed trains.

At Paris' Gare Saint Lazare, which serves the French capital's western suburbs and the northwestern Normandy and Brittany regions, commuters waited on crowded platforms for their trains. Only about half of regularly scheduled trains were running out of the station Tuesday.

Caroline Mesnard, a 29-year-old teacher said she expected her commute to take about twice as long as usual — as it has since last Tuesday's start of the open-ended strike on France's trains.

"All I can say is that after eight days, it's beginning to get a bit tiresome," said Mesnard. "I'm really tired, but there's nothing to be done but hang on and wait for this to end."

In the Mediterranean port city of Marseille, strikes by garbage collectors have left heaps of rubbish piled along city sidewalks. But still, the piles of rotting garbage don't appear to have diminished labor union support in a city that has long had an activist reputation.

"Transport, the rubbish, the nurses, the teachers, the workers, the white collar, everyone who works, we should all be united. If there is no transport today, we're not all going to die from it," said 55-year-old resident Francoise Michelle.

Sarkozy has stressed that 62 is among the lowest retirement ages in Europe, the French are living much longer and the pension system is losing money.

"This reform is essential, France is committed to it, and France will carry it out," Sarkozy said Monday in the Normandy beach resort of Deauville.

The measure is expected to pass a vote in the Senate this week. Slated to take place on Wednesday, it's been push back until Thursday so lawmakers have the time to examine hundreds of amendments brought by opposition Socialists and others.

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Associated Press writer Angela Charlton and APTN cameraman Oleg Cetinic in Paris contributed to this report.