French police have broken a union blockade at the oil refinery which supplies the main international airport in Paris.
Demonstrators throughout France are protesting against the government's plans to raise the retirement age from 60 to 62.
The Total refinery at Grandpuits is seen as critical for supplying fuel to Paris and the main airports at Charles de Gaulle and Orly.
Clashes broke out hours after riot police removed a barricade outside the refinery early on Friday. Two people have been injured.
Union official Charles Foulard has described the action as a scandal after police acted in the middle of the night, the BBC reports.
It is one of 12 facilities that have been blocked by striking workers and protesters for the past 10 days.
Earlier this week, president Nicolas Sarkozy ordered authorities to lift the blockade after thousands of petrol stations across France ran dry.
The Senate is due to vote on Friday on pension reforms which sparked the protest action.
The government plans to increase the retirement age from 60 to 62 and the full state pension age from 65 to 67.
The unions have called for two further days of protests on top of rolling strikes.