(BBC) -- Rioting has continued in France for a 13th consecutive night, despite emergency powers aimed at restoring order coming into force.

More than 500 cars had been torched by 0400 (0300GMT), police said. Around 200 people were arrested.

But police said the levels of violence across the country were lower than the previous night.

The northern city of Amiens was the first to impose an overnight curfew under the new emergency plan.

The special decree giving local authorities and police emergency powers to deal with rioters came into force at midnight.

Two Paris suburbs, Savigny-sur-Orge and Le Raincy, as well as the historic city of Orleans, have already declared separate curfews not covered by the law.

Despite this, incidents were reported in several areas:

• The entire public transport network was shut down in the central-eastern city of Lyon after a Molotov cocktail was thrown at a train station
• A gas-powered bus exploded in the suburbs of the south-western city of Bordeaux after it was hit by a Molotov cocktail
• Youths in the nearby city of Toulouse threw firebombs at police and set fire to cars

Paris, where the rioting began nearly two weeks ago, was relatively calm with some isolated cases of arson and a dozen arrests, the police said.

Shortly before the decree came into effect, Interior Minister Nicolas Sarkozy, on a visit to Toulouse, said police were reporting a "fairly significant fall" in violence.

State of emergency

The emergency powers were approved in a special cabinet meeting earlier on Tuesday.

They allow a state of emergency to be declared in defined areas, restricting the movement of people and vehicles.

Police are entitled to carry out house searches and ban public meetings.

Mr Sarkozy, who announced the measures, said: "The violent events that happened in our territory, and the people responsible [for the violence] will be arrested and punished".

But some opposition parties, and the French magistrates association, have described the measures as a danger to civil liberties.

Minors are subject to the law between 2200 and 0600 (2100 and 0500 GMT) unless accompanied by an adult, and are also banned from buying petrol.

Social improvements

The nightly protests have gripped deprived areas where unemployment is rife and residents complain of racism and discrimination.

Prime Minister Dominique de Villepin said on Tuesday the restoration of law and order in those suburbs would take time and hard work.

And he also outlined plans to improve opportunities for young people through jobs and education programmes and create an agency to combat racial discrimination.

"The republic is at a moment of truth," he said. "What is being questioned is the effectiveness of our integration model."

The unrest was first sparked by the deaths in the run-down Paris suburb of Clichy-sous-Bois of two youths, who were accidentally electrocuted at an electricity sub-station.

Locals said they were being chased by the police, but the police deny this.

The new emergency powers handed to local authorities have been invoked under a 1955 law.

The law was originally passed to combat violence in Algeria in its war of independence against France from 1954-62. It was also used in New Caledonia in 1985.

This is the first time the law has been implemented in mainland France.