The Senate on Wednesday passed the extension - a day after a similar vote in the lower house.

The laws allow local authorities to impose curfews, conduct house-to-house searches and ban public gatherings.

The government says it still needs extra powers to end almost three weeks of civil unrest in France's poor, largely immigrant suburbs.

Almost 9,000 cars have been torched and about 3,000 people have been arrested.

Violence continued across France on Tuesday night but fewer cars were set on fire than during previous nights.

Nationwide, 163 cars were burnt - almost down to the levels seen before the riots began last month.

At the height of the violence, more than 1,400 vehicles were destroyed in a single night.

National Police Chief Michel Gaudin said on Tuesday the decline showed France was "getting back to normal".

But Prime Minister Dominique de Villepin told parliament "we cannot accept that more than 200 cars burn each night".

'Polygamy problems'

The violence has spread from Paris across French towns and cities, mostly in areas with a high concentration of ethnic minorities.

The riots began when two boys of North and West African origin were electrocuted in a Paris suburb after running from police, believing they were being chased.

French Foreign Minister Philippe Douste-Blazy told the BBC that France has been going through a "very deep crisis due to the crisis of immigration and the failure to integrate".

He also pointed to the problem of racism.

Meanwhile, senior officials from President Jacques Chirac's centre-right party have suggested that polygamy is one factor in the riots, arguing children of polygamous families have less of a father figure and are more likely to live in overcrowded conditions.

"Polygamy... prevents people being educated as they should be in an organised society. Tens of people cannot live in a single flat," Bernard Accoyer, leader of the Union for a Popular Majority (UMP) in the National Assembly lower house of parliament, told French radio.

Polygamy is illegal in France but until 1993, it was possible for immigrants to bring more than one wife from their home country to join them.

The lower house passed them by a 346-148 majority, and the Senate by 202-125.

The laws date from the Algerian war of independence in the 1950s.

The Socialist opposition attacked plans to extend the state of emergency, pointing out that few local governors had chosen to impose it.