French authorities forced strike-shuttered fuel depots to reopen to ensure gasoline supplies, and the interior minister threatened Wednesday to send in paramilitary police to stop rioting on the fringes of protests against raising the retirement age to 62.

Youths wearing hoods and scarves on their faces rampaged through the Paris suburb of Nanterre, breaking shop windows and hurling stones at riot police. The town has seen clashes in recent days centered on a high school that joined the protests.

Months of largely peaceful demonstrations against the pension reform have taken a violent turn in recent days. The plan is slated for a vote in the Senate on Thursday, but labor unions want the government to renegotiate, saying the bill threatens the country's hard-earned social protections.

President Nicolas Sarkozy and his government have stayed firm, insisting it is essential to saving the money-losing pension system. Countries around Europe are also facing public resistance as they try to tame government debts that have threatened the euro currency.

With nearly a third of France's gas stations dry Tuesday, authorities stepped in overnight to force open three fuel depots in western France blocked by striking workers for days, Interior Minister Brice Hortefeux said. He said the operations saw no violence.

"The right to strike does not give anyone the right to prevent people from working or the right to block things, or the right to prevent travel," Hortefeux said.

He warned that the fuel depot blockades threaten emergency services and could have grave consequences for the entire French economy and public health and safety. He described an "infernal spiral" of consequences when nurses and bus drivers can't get to work.

"These acts are not only unacceptable, but they are also irresponsible," he said.

French unions have a long tradition of street protests, but the current strife is particularly worrisome because it has touched the vital energy sector and is drawing often volatile youth into the mix.

Hortefeux warned rioters that "the right to protest is not the right to break things, the right to set things on fire, the right to assault, the right to pillage."

"We will use all means necessary to get these delinquents." That includes the GIGN paramilitary police, he said.

Over the past week, 1,423 people have been detained for protest-related violence, he said, more than a third of them Tuesday. Of those, 123 are facing legal action. He said he ordered police to look at video surveillance to find more perpetrators, suggesting more arrests could be ahead.

He said 62 police officers have been injured in the violence over the past week.

In Nanterre on Wednesday morning, about 100 students blocked the school entrance and part of highway in front of the school, while a "tranquility team" of about 30 adults in special red jackets sought to keep things calm.

Then about 100 other youths arrived and started darting through the town streets, smashing store windows and throwing stones. Some store owners lowered metal blinds to avoid looting. Nine police vans were parked in the surrounding area.

The sidewalks of Nanterre were littered with glass from bus shelters and illuminated signs that had been smashed Tuesday. All the vehicles were removed Wednesday from the street in front of the school, because a car had been torched there the day before.

This week's clashes revived memories of student unrest in 2006 that forced the government to abandon another highly unpopular labor bill. And the specter of 2005 riots that spread through poor housing projects nationwide with disenfranchised immigrant populations is never far away.

Students plan new protests Thursday, with a demonstration in Paris hours before the Senate is expected to approve the measure. The bill would raise the retirement age from 60 to 62 to prevent the pension system from going bankrupt as citizens live longer and a diminishing pool of young workers pay into the system.