Rioters in the French city of Grenoble shot at police and torched cars overnight as the authorities struggled to restore order after two days of violence.
The riot on the outskirts of the Alpine city echoed civil unrest that exploded in France in 2005, mainly in the rough suburbs that ring many of the country's big cities.
In Grenoble, the violence flared on Friday after a local resident suspected of robbing a casino was killed in an exchange of fire with police in nearby Uriage-les-Bains.
Yesterday, hundreds of police and elite national troops patrolled the streets as unrest continued overnight.
About 16 cars were burned and in one incident, rioters shot at a police car from a building, said Brigitte Julien, a police official.
"We will not allow delinquents to rule here," said Julien. "If needed we will stay in the streets every day and every night... we must stop these attacks."
The mayor of Grenoble, Michel Destot, said police had arrested 19 people for offences including drug trafficking and arms possession. He described the suburb as largely immigrant and poor, with an unemployment rate of more that 30 percent.
"Villeneuve is a working-class neighborhood where the difficulty is that the population is not mixed enough and people have been weakened by the economic crisis," he said.
"There has been a rise in the underground economy and a relatively small gang of youth have imposed their law and created a climate of extreme insecurity."
Many French cities are encircled by suburbs plagued by high unemployment, crime, poor public services and drug trafficking.
The government estimates there are as many as 500-600 such high-rise neighbourhoods. They are home to up nearly five million people, many of immigrant origin.
The government is trying to reassert a visible police presence in these neighbourhoods but some of them have become virtual no-go areas for law enforcement, officials say.
Many of them were built in the 1960s and 1970s to house waves of immigrants from North Africa and sub-Saharan Africa who had been recruited to work in French industry.
The government began to restrict immigration in the mid-1970s but failed to build enough housing for the newcomers or to disperse the immigrants around the country and into the population, turning many of the new suburbs into ghettoes.
The official unemployment rate among non-French nationals is 20 per cent - twice the national average. Most of the residents of these suburbs have French citizenship, many are second or third generation.
The earnings available in the drugs trade dwarf what young people could hope to earn from legal work, and people are often sucked into the drugs trade from an early age, police say.
Officials estimate that a 13-year-old can earn €150 euros a day acting as a look-out for drug.
The mayor deplored the fact that police numbers had thinned in Grenoble to 600 from 720 in recent years, saying that police needed to be more present in communities like Villeneuve.
"The national government has promised to re-establish calm in Villeneuve," said Destot. "But to really improve the situation in these areas, we need a sustained policy of urban renewal over the long-term."
Reuters