Fuel shortages rattled drivers and businesses across France on Saturday as protesters marched for the fifth time in a month to protest reforms that would raise the minimum retirement age to 62.
Strikes at refineries and fuel storage depots over the past week by workers opposed to the plan have forced some gas stations to close because the pumps are empty.
The protests have also restricted the fuel supply to Paris airports.
There are fears the country's main airport, Charles de Gaulle, could run out of fuel by next week and that Orly airport only has enough for the next two to three weeks.
"I don't say we can't guarantee beyond Tuesday … we will find other solutions," a ministry spokesman told The Associated Press.
He said France had not yet resorted to emergency fuel imports from neighbouring Italy or Spain.
Finance Minister Christine Lagarde has urged people not to panic, but lineups could be seen at gas stations in cities across France on Saturday.
"Today, there is no reason, no reason … to panic," she told BFM-TV on Saturday, noting that only 230 of the country's 13,000 gas stations were out of fuel. "There are weeks of reserve."
High school students were front and centre at several of Saturday's rallies. Students fear the reforms will end up worsening youth unemployment as older workers stay in their jobs longer.
On Friday, police fired tear gas at protesters in the city of Lyon, where about 1,000 students had blocked access to several schools.
Unions had called for more than 200 demonstrations on the fifth consecutive day of mass protests.
Frequent strikes in the last few weeks have hobbled French trains and airports, closed schools and docks, and left garbage piling up in the southern port of Marseille.
President Nicolas Sarkozy wants to raise the minimum retirement age from 60 to 62, and from 65 to 67 for a full state pension in order to help control the government's ballooning debt.
Even with the two-year change, France would still have among the lowest retirement ages in the developed world.