PARIS - French oil workers expanded a strike Friday over government plans to raise the retirement age, while European discontent over belt-tightening measures flared up in Portugal, Italy and Greece.

All of France's oil refineries were on strike, and the government deployed police to force the reopening of several fuel depots around the country that had been blocked, raising concerns of possible gas shortages.

As French students clashed with police and labour leaders planned more nationwide demonstrations on Saturday and Tuesday, discontent over government austerity plans seemed to spread across the continent.

Countries throughout Europe are attempting to cut spending and raise revenue to bring down deficits and debts that hit record levels after the 2008 financial crisis resulted in the worst recession in 70 years. Labor leaders, students and civil servants are fighting back.

Thousands of students and teachers staged demonstrations in a dozen cities across Italy to protest planned cuts in higher education, while Portugal's minority government faced a battle in parliament over its plan for abrupt tax hikes and deep spending cuts.

Meanwhile, a labour dispute that kept out thousands of visitors for three days from debt-ridden Greece's most famous monument, the Acropolis, was ended only after hundreds of Culture Ministry employees were forcibly dispersed by riot police using tear gas.

In France, workers at all 12 fuel-producing refineries were on strike after two plants owned by Exxon Mobil and Petroplus voted to join the protest Friday, said Charles Foulard, a union co-ordinator at oil company Total SA.

France's transport minister authorized oil companies to use some of their reserves after trucking companies complained of difficulties fueling their vehicles. Dominique Bussereau told French radio station RTL that the country's stocks of fuel meant there was no reason for drivers to fear a gas shortage.

Nonetheless, police moved in to reopen fuel depots near Marseille and Clermont-Ferrand that had been blocked. Access to an oil port near Bordeaux that had been blocked since Thursday was reopened after talks between strikers and a local official.

Truck drivers joined in the protests. "We will block everywhere we can block," Patrick Van Craeynest of the CGT truck drivers' union said on France-Info radio."

French students, whose protests and sporadic clashes with police have caught the government's attention, were on the streets Friday, but fewer in number compared to previous demonstrations.

About 1,000 high school students demonstrated in downtown Lyon. Students overturned garbage bins, smashed bus stops, set fires to stacks of free newspapers.

More than 150 young people were detained Friday at demonstrations around the country, according to the Interior Ministry.

The interior minister urged police to use restraint in containing student protests, after a 16-year-old was hospitalized Thursday with serious face wounds from a rubber bullet fired by police in a Paris suburb of Montreuil.

The students and labour unions see President Nicolas Sarkozy's pension reform -- raising the retirement age from 60 to 62 -- as an attack on their well-deserved social protections. The government says it is the only way to save the money-draining pension system and insists that people have to work longer because they are living longer. The Senate is to vote on the measure Wednesday.

The Education Ministry said 306 high schools were affected to various degrees by strikes, down from 342 on Thursday. There are around 4,300 high schools in France.

Several hundred students blocked the entrance to Lycee Voltaire high school near Paris' famed Pere Lachaise cemetery, as they had done every day since Tuesday.

"We want to tell Sarkozy that he is really in trouble, the youth are ready to mobilize with the rest of the 70 per cent of the French society that is against this reform," said Benjamin Vernay, 17, a student leader at the school.

While the protesting students won't reach retirement age for decades, the government is keeping a close eye on their rallies because student protests have brought down major government reforms in the past.

France's transportation system was running more smoothly Friday, after severe disruptions hit air, rail and road traffic earlier in the week.

Airports were functioning normally, as was Paris' public transport system, with the exception of the RER B suburban train line that connects the capital to its two main airports. The line was operating at 50 per cent of normal levels, the RATP public transport authority said.

The SNCF national railway operator said traffic on Eurostar trains between Paris and London was normal. Around two-thirds of the TGV high-speed trains departing from and arriving in Paris were running, the SNCF said.

However, the train authority recommended that travellers heading to southern France postpone their trips because of "local difficulties," with regional train service running at around 50 per cent.