This may be the start of something big: Car bomb targets French Muslim leader. (Hat tip: Kragar.)

Hours after up to 40,000 Muslims marched against a planned ban on Islamic headscarves in state schools, a carbomb attack on a newly appointed prefect of Algerian origin dramatically underlined the scale of France’s problem in assimilating its immigrant Muslim community.

The 4.30am explosion in the western city of Nantes destroyed the car of Aissa Dermouche, 57, an academic and educationalist who was appointed the prefect - or top state representative - of the Jura region last Wednesday.

“There is no doubt that this was a criminal act,” said Jean-Marie Huet, the Nantes state prosecutor. Although the car was empty at the time and no one was hurt, Mr Huet said the plainly well-prepared attack “targeted the new prefect personally, and the symbol that he represents”.

Mr Dermouche will be responsible for law and order in the region. His was not the first high-profile post to be awarded to a member of an immigrant minority, but it came amid a debate about how France can better assimilate its 5 million-strong Muslim community.

President Jacques Chirac, defending the values of a republic that supposedly treats everyone equally regardless of their background, has knocked the notion of positive discrimination and spoke last week only of the “deserved promotion” of a “talented individual of immigrant origin”.

Police said the explosive, whose nature has yet to be determined, could have been planted by Islamic radicals upset at Mr Dermouche’s “selling out”, or by far-right militants.