Thousands of police guarded the Eiffel Tower, the Champs Elysees and train stations, as part of emergency measures enacted in response to text messages and Internet postings that called for "violent actions" in Paris. National Police Chief Michel Gaudin said police were taking "every precaution," including banning certain public gatherings, a day after the 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." However, no trouble anywhere in Paris had been reported overnight Saturday to Sunday. 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 Saturday night 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. In separate incidents Saturday night in the southern city of Carpentras, rioters rammed burning cars into the side of a retirement home and a school, national police spokesman Laurent Carron said. A primary school and linen store were also set ablaze in Carpentras, he said. Police counted 315 cars torched and said 161 people were arrested across France overnight as of 4 a.m. (0300 GMT). A police officer was injured after he was hit with a metal ball dropped from an apartment building in the northern Paris suburb of La Courneuve, Carron said. Arsonists also set an electronics store on fire Saturday night in Blangnac, on the outskirts of Toulouse, the regional government said. 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 tough 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 Oct. 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 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-Saturday, compared to a total of 502 nationwide. The overall figure was slightly higher than 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-Saturday - 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. 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.