PARIS, France (AP) -- Emergency security measures went into effect Saturday in Paris, with 3,000 police patrolling train stations, the Eiffel Tower and the Champs-Elysees to prevent France's worst unrest in decades from spreading to the capital.National Police Chief Michel Gaudin said police were taking "every precaution," including banning certain public gatherings, a day after calls for "violent actions" Saturday evening in Paris were posted on Internet blogs and sent in text messages to cell phones."This is not a rumor," Gaudin told a news conference, citing Paris' best-known landmarks among potential targets. "One can easily imagine the places where we must be highly vigilant."Several hours after nightfall, no trouble anywhere in Paris had been reported.Unrest has weakened in intensity since the government declared a state-of-emergency Tuesday, empowering local authorities to invoke exceptional security measures such as curfews if deemed necessary.Despite heightened security around the country, new violence broke out early Saturday evening in the southeastern city of Lyon. Police fired tear gas to disperse stone-throwing youths at the city's historic Place Bellecour. It was the first time in 17 nights of unrest across France that youths and police clashed in a major French city.Just hours earlier, regional authorities had imposed a weekend curfew on Lyon, France's third-largest city, that barred youths under 18 from being outside without adult supervision between 10 p.m. and 6 a.m.Some 40 towns, suburbs and smaller cities have imposed curfews on minors to clamp down on violence that started Oct. 27 in a Paris suburb and has grown into a nationwide insurrection marked by extensive arson and clashes with police.Paris police took the exceptional step of banning all public gatherings that could "provoke or encourage disorder" from 10 a.m. Saturday to 8 a.m. Sunday. Police spokesman Hugo Mahboubi said it had been at least a decade and possibly longer since authorities had imposed any similar ban on gatherings in the French capital.As unrest continued, calls for peace and political change were mounting.Police allowed an evening demonstration in Paris' Latin Quarter, which drew several hundred people protesting against the state-of-emergency measures. Many of the protesters were left-wing political groups and members of Communist-backed unions. They called for the resignation of Interior Minister Nicolas Sarkozy, who has been accused of inflaming the violence by calling troublemakers "scum."Under tight police surveillance, protesters called the strict new measures a "provocation" that would not resolve violence or answer the long-term problems that caused the unrest. A similar rally in the southern city of Toulouse drew about 700 people.The violence first started in the northeastern Parisian suburb Clichy-sous-Bois on October 27. About 100 youths rioted to protest the accidental deaths of two Muslim teens, who were electrocuted while hiding from police in an electricity substation. It quickly triggered rioting in low-income housing projects across the country that have been centers for unemployment and alienation.The unrest has forced France to confront its failure to integrate minorities and the anger simmering among its large African and Arab communities.Late Friday, two gasoline bombs were tossed into a mosque in the southern city of Carpentras, slightly damaging the foyer. It was not immediately clear whether the attack was linked to the unrest.President Jacques Chirac asked investigators to find those behind the incident in Carpentras, a town grimly remembered for a 1990 neo-Nazi attack on a Jewish cemetery that sparked national outrage.Police said that unrest was now concentrated outside of the Paris region, where 86 vehicles were burned overnight Friday, compared to a total of 502 nationwide.The overall figure was slightly higher than during the previous night, but a significant drop from the 1,400 cars incinerated in a single night of mayhem a week earlier.Arson attacks were reported in 163 towns around France overnight Friday and early Saturday morning -- about half the towns hit by violence a week earlier, the national police chief said.The riots have been marked by hundreds of nightly arson attacks on vehicles. Schools, gymnasiums, warehouses and public transport also have been targeted for arsons.Two police officers were injured, one burned in the face by a gasoline bomb while trying to put out flames of a burning vehicle in the Aisne region, Gaudin said.Overall, 2,503 people have been detained since the start of the unrest, with 364 of them convicted in expedited trials. Nearly 460 minors have gone before juvenile courts, 103 of whom were in the process of being charged, the Justice Ministry said.Copyright 2005 The Associated Press. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.