Policemen patrol street in Grigny, south of Paris, early Wednesday

French authorities say violence flared for the 13th night in several cities despite night-time curfews, but the number of attacks dropped sharply.

Official say rampaging youths burned more than 600 vehicles across the country, about half the number set aflame night before. Police say 204 people were arrested in the latest violence, which has been carried out mainly by Muslim youths of North African descent.

A state of emergency went into effect at midnight permitting such cities as Amiens, Orleans and the Paris suburb of Savigny-sur-Orge to declare curfews.

In the southern city of Lyon, officials shut the entire subway system after a firebomb exploded in one station late Tuesday. No injuries were reported.

Prime Minister Dominique de Villepin Tuesday announced a number of measures to address what many French say are the main causes of the riots - youth unemployment, poor schools and discrimination.