PARIS (AFP) - – Strikes threatening to paralyse France's economy looked set to rumble on into Wednesday after a million people took to the street for their right to retire at 60 and fuel shortages began to bite.

Clashes erupted between youths and riot police in several towns Tuesday and shops in the city of Lyon were looted as workers and students came out in force around the country to protest President Nicolas Sarkozy's unpopular reform.

Sarkozy refused to back down however and leading unions in some sectors including airports called for stoppages to continue on Wednesday, while oil refineries remained blocked, hit by a week of strikes.

The DGAC aviation authority said a quarter of flights from Orly, Paris's second-biggest airport, would be cancelled on Wednesday morning but did not detail further disruption at the main hub, Charles de Gaulle.

Facts: France's biggest demos

Around one in three flights at Roissy-Charles de Gaulle and regional airports were cancelled on Tuesday, while one in three filling stations ran out of fuel, the government said.

The latest day of protests, the sixth since September, drew around 1.1 million people onto the streets, police said, slightly fewer than the 1.23 million on the last comparable day, October 12.

The CGT, France's biggest union, told AFP it estimated overall turnout at 3.5 million, equal to its estimate for October 12. Unions' estimates have habitually been several times higher than those of police.

With more than 200 protests on Tuesday, all 12 French oil refineries shut down by strikes and truckers blocking roads, Sarkozy instructed the cabinet to draw up a plan to stop France grinding to a standstill.

Environment and Transport Minister Jean-Louis Borloo said that "a little under 4,000 petrol stations are awaiting deliveries." There are around 12,500 filling stations in France.

French fuel and heating federation FF3C said the "extremely worrying" situation "should definitely be called a shortage", while the International Energy Agency said France has "sufficient stocks" to deal with the situation.

Authorities in Normandy requisitioned 12 petrol stations for use by rescue and emergency services, while Prime Minister Francois Fillon said a third of departments or local administrations were experiencing fuel shortages.

Fillon chaired a meeting with several ministers and oil industry officials on how to deal with the crisis and ministers later held talks with Sarkozy.

Fillon's office said the government would ensure access to fuel depots, many of which are blocked by strikers, and that distributors would pool their fuel and trucks to help needy stations.

The interior minister promised tough action as clashes erupted anew outside a secondary school in Nanterre, near Paris, where youths burned a car and threw rocks at riot police for the second day in a row.

Police fired tear gas and arrested nine youth protestors in Lyon who had overturned cars and set one alight. At least five shops were later looted, police said.

Nine people were arrested Tuesday in Paris, police said.

The ministry said that 1,158 troublemakers had been arrested at demonstrations since the start of the week, 163 of them on Tuesday morning.

The powerful CGT union's transport section called for their strike action to be renewed on Wednesday, encompassing airport staff, air traffic controllers, public transport workers and employees of national railways operator SNCF.

Unions want to force Sarkozy to abandon a bill to raise the minimum retirement age to 62, which is in the final days of its journey through a parliament in which the right-wing leader enjoys a comfortable majority.

Most French back the current protests, with a poll published Monday in the popular Le Parisien daily showing that 71 percent of those asked expressed either support or sympathy for the movement.

A poll published Tuesday showed that Sarkozy's approval rating dropped this month to its lowest in three years at 30 percent, two percentage points less than when the main pension protests started in September.