When Nadir Dendoune was growing up in the 1980s, his home town of L'Ile Saint-Denis, north of Paris, was a fairly diverse place. "We were all poor, but there were French people, East Europeans, as well as blacks and Arabs," says Mr Dendoune, 33, an author and something of a celebrity in his estate. Two decades on, the complexion of the place has changed. "On my class photos more than half the kids were white," he says. "On today's pictures only one or two are." L'Ile St-Denis is among the "suburbs" around French cities where immigrants, notably from former North African colonies, have been housed since the 1960s. Blighted by bad schools and endemic unemployment, the suburbs are hard to escape. The immigrants' children and grandchildren are still stuck there - an angry underclass that is increasingly identified through religion. Ten years ago these youths were seen as French "Arabs". Now most are commonly referred to, and define themselves, as "Muslims". Many countries have ethnic and religious enclaves. But in France they cause particular alarm, for three reasons. First, they are not supposed to exist in a nation that views itself as indivisible, and able to assimilate its diverse components.

Separatism, the French are told, is a plague afflicting the Anglo-Saxon multicultural model.

The government bans official statistics based on ethnicity or religion. As a result, no one knows exactly how many Muslims live in the country - at least five million is the best guess. Ghettos also threaten another tenet of French identity - secularism. As the country celebrates the centenary of the separation of Church and State, Islam is seen as the biggest challenge to the country's secular model in the past 100 years. Thirdly, the worldwide rise of Islamic militancy strikes fear in the heart of a country that is home to Western Europe's biggest Muslim community. French police know that there is no shortage of potential jihadis in the country. The assertiveness of French Islam is seen as a threat not just to the values of the republic, but to its very security. A different view: Is such alarm justified? The view from the suburbs invites a nuanced, and ultimately sanguine, assessment. Some groups do advocate cultural separation for Muslims - but they do not speak for many. Far more common is the attitude of Nour-eddine Skiker, a youth worker near Paris: "I feel completely French. I will do everything for this country, which is mine." Mr Skiker's Moroccan origins mean a lot to him. But, like many youths in the suburbs, he sees no contradiction between being French and having foreign roots. The main problem is that many French people do, says writer Nadir Dendoune. "How am I supposed to feel French when people always describe me as a Frenchman of Algerian origin? I was born here. I am French. How many generations does it take to stop mentioning my origin?" And crucially, the suburbs are full of people desperate to integrate into the wider society. "I do not know a single youth in my estate who does not want to leave," Mr Dendoune says. France's Muslim ghettos, in short, are not hotbeds of separatism. Neither do they represent a clear challenge to secularism - a doctrine all national Muslim groups profess to support. "We have no problem with secularism," says Lhaj Thami Breze, president of the Union of Islamic Organisations of France (UOIF). He argues that by establishing state neutrality in religious matters, the doctrine allows all religions to blossom.

Islam has adapted to local laws - from Indonesia to Senegal - and is adapting to France, says Azzedine Gaci, who heads the regional Muslim council in Lyon.

This is not just the leaders' view. A 2004 poll suggested that 68% of French regarded the separation of religion and state as "important", and 93% felt the same about republican values. Suspicious minds: All observers agree that jihadism does pose a direct threat to the country. The fact that - in France as elsewhere - the militants speak for a tiny minority of Muslims does not make the threat less severe. But as Islam expert Olivier Roy notes, bombers should not be seen as the vanguard of the Muslim people. Jihadis everywhere, he says, are rebelling both against the West and their own community. The great majority of Muslims resent the extremists in their midst - although many in France do not recognise this. Yazid Sabeg, an industrialist and writer, says the French have "a real problem" with both Arabs and Islam and equate both with extremism. The most worrying aspect of the separation between French Muslims and the rest of society is that it breeds suspicion on both sides. "We must tell youths that France does not want to hold them down," says Rachid Hamoudi, director of the Lille mosque in northern France. "We must ensure that the community trusts its country, and vice-versa. If you get to know me, you will get to trust me. If I get to know you, I will trust you."

French Prime Minister Dominique de Villepin has held a series of crisis meetings, after a seventh night of rioting in Paris suburbs. Youths opened fire on police and set buildings and vehicles ablaze. A criminal investigation and an internal police inquiry have been opened into the deaths of two youths which triggered the rioting. Mr de Villepin condemned the violence and said restoring order was his "absolute priority". Bouna Traore, aged 15, and Zyed Benna, 17, were electrocuted at an electricity sub-station. Local people say they were fleeing police, a claim the authorities deny. Mr de Villepin cancelled an overseas trips in the face of the growing dissatisfaction with the government's failure to quell the violence. Speaking to French MPs, he said that law and order would have the last word. "I refuse to accept that organised gangs are laying down the law in certain neighbourhoods," he said. On Thursday afternoon, he held cross-party crisis talks with Interior Minister Nicolas Sarkozy, other ministers, MPs and mayors of the some of affected towns. Mr Sarkozy earlier met the dead teenagers' families. Mr de Villepin and Mr Sarkozy and are likely rivals for the presidency in 2007, and their different approaches to the rioting had split the cabinet. Mr Sarkozy has caused controversy by labelling the rioters as "scum" and saying many of the suburbs need "industrial cleaning", but Mr de Villepin has preached a more conciliatory message, urging ministers not to "stigmatise" vast areas.

Running clashes: Wednesday night's violence erupted in 10 areas across the Paris department of Seine-Saint-Denis, home to poor, largely immigrant communities with high levels of unemployment. At least 15 people were arrested and nine were injured. Locals officials said rioters set fire to 177 vehicles across the region. In the flashpoint town of Aulnay-sous-Bois, youths set fire to a car showroom and damaged two primary schools, a post office and a shopping centre At a supermarket in Bobigny on Thursday, staff were sweeping up broken glass. "If this continues, I'll have to close. Clients are afraid. There's normally lots of people here at this time of the day," a local cobbler told the Reuters news agency. Two live rounds were fired in the town of La Courneuve, and fire fighters in Saint-Denis and Noisy-le-Sec were also shot at, a senior local official said. There was violence in another northern area, Le Blanc Mesnil, where a French TV truck was overturned and burned. In the western Hauts-de-Seine department, a police station was bombarded with petrol bombs, the AFP news agency reported. The situation also remained tense in Clichy-sous-Bois, where the teenagers died, and where the rioting first broke out. In recent days there have also been incidents involving groups of youths in other departments near Paris, including the Val-d'Oise, Seine-et-Marne and Yvelines. Francois Masanet, secretary general of the French police union, described the situation as "dramatic", and warned that the violence could escalate. Right-wing French MP Philippe de Villiers told RTL radio that the problem stemmed from the "failure of a policy of massive and uncontrolled immigration". Minister of Social Cohesion Jean-Louis Borloo said the government had to react "firmly", but added that France must also acknowledge its failure to have dealt with anger simmering in poor suburbs for decades. French politicians are facing up to the reality that many of the mainly immigrant populations in cities have long been in a state of chronic tension, says the BBC's European Affairs correspondent William Horsley. Immigrants and their offspring make up 10% of France's population, but many are without French citizenship and the right to vote. They also suffer the highest rate of unemployment, and their relations with the police are generally difficult or hostile, our correspondent says. Dalil Boubakeur, the head of the Paris mosque and the president of the French Council for the Muslim Religion, said living conditions for Muslim immigrants in the suburbs were unacceptable. They "must be given the conditions to live with dignity as human beings", not in "disgraceful squats", he said.