A ban on saying prayers in the street, a practice by French Muslims unable to find space in mosques, has come into effect in the capital, Paris.
Interior Minister Claude Gueant has offered believers the use of a disused fire brigade barracks instead.
The phenomenon of street prayers, which see Muslims spreading mats on footpaths, became a political issue after far right protests.
France is home to the biggest Muslim minority in Western Europe.
By some estimates, as many as six million French people, or just under 10% of the population, are Muslims, with origins in France's former North African colonies.
Their integration has been a source of political debate in recent years, and earlier this year France became the first EU state to ban the wearing of the Islamic veil in public.
The new ban came into force at midnight (22:00 GMT) on Thursday, in time for traditional Muslim Friday prayers.
Speaking earlier this week to Le Figaro, Mr Gueant said about 1,000 people were using two streets in the capital's multi-ethnic Goutte d'Or district for prayers.
He said an agreement had been reached with two local mosques for the state to rent out the disused barracks on Boulevard Ney with floorspace of 2,000 sq m (yds) for three years.
To encourage believers to use the new space, prayers would not be held inside the existing mosques for the first few weeks.
He said he did not believe force would have to be used to impose the ban because dialogue was "bearing fruit".
An overseer at the barracks said the space, with a capacity of 2,000, was full.
"It's the beginning of a solution," Sheikh Mohammed Salah Hamza told Reuters news agency. "The faithful are very pleased to be here. "
"I think it's great. It's good. Before they used to pray outside and that wasn't good at all," Kaddar Abdelkader, who used to pray in the street, told the BBC.
Mr Gueant said similar problems with street prayers existed in two other cities, Marseille and Nice.
Far right protests at the "Islamisation" of the Goutte d'Or district began last year and in December the leader of the French National Front, Marine Le Pen, accused Muslim fundamentalists of using prayers for political ends.
She controversially compared the practice to the Nazi wartime occupation of France.