French Interior Minister Christophe Castaner said Friday that a three-week-old rebellion over taxes had spawned "a monster", as Paris braces for further violent "yellow vest" protests this weekend.
On the eve of a fourth set of demonstrations in the capital in as many weeks, Castaner vowed "zero tolerance" towards those hoping to enact a repeat of last weekend's destruction and mayhem.
"These past three weeks have seen the birth of a monster that has escaped its creators," a grave-looking Castaner told a press conference.
"It's time now for dialogue," he urged.
Last Saturday's riots in Paris, where the Arc de Triomphe war memorial was sacked, dozens of cars torched and shops looted, were the worst in decades, plunging President Emmanuel Macron's government into a deep crisis.
Shops around the famous Champs-Elysees boulevard -- epicentre of last week's battle between police and protesters -- were battening down the hatches on Friday.
The sound of hammers and power tools rang out along the Grande Armee avenue as shops boarded up windows and emptied their stock.
"We can't take the risk," said a manager at a Ducati motorcycle dealership, as employees loaded luxury Italian racers onto trucks for safekeeping.
Last week, the store was looted of 120,000 euros' ($136,000) worth of merchandise.
Leading museums and landmarks, including the Eiffel Tower, Arc de Triomphe, Louvre and Musee d'Orsay, have also said they will remain closed on Saturday.
The US embassy issued a warning to its citizens in Paris to "keep a low profile and avoid crowds".
Macron this week gave in to on some of the protesters' demands for measures to help the poor and struggling middle classes, including scrapping a planned increase in fuel taxes.
But the "yellow vests" are holding out for more.
The government has warned peaceful protesters to stay away from Paris on Saturday and vowed a tough response in the event of trouble.
Prime Minister Edouard Philippe said 8,000 police would be deployed in Paris, out of 89,000 nationwide, and that a dozen armoured vehicles would be stationed around the capital -- a first in the city in 13 years.
Police were already battling accusations Friday of being heavy-handed, with a video of high-school pupils kneeling on the ground with their hands behind their heads causing widespread outrage.
"Whatever wrong was done, nothing justifies this filmed humiliation of minors," Socialist leader Olivier Faure tweeted.
"There is no need to pour even more oil on the flames," Faure warned after the mass round-up of teens following protests at a school in the Paris suburb of Mantes-la-Jolie, where two cars were burned.
Laurent Saint-Martin, a senior member of Macron's Republic On The Move (LREM) party, said around 40 of the students were masked and carrying equipment for use in vandalism and arson.
But he too described the videos as "shocking".
The "yellow vest", named after the safety jackets worn by demonstrators, began blocking roads, fuel depots and shopping centres around France on November 17 over fuel price hikes.
Protests at dozens of schools over stricter university entrance requirements, and a call by farmers for demonstrations next week, have added to a sense of general revolt.
Four people have died so far in accidents during the yellow vest protests and political leaders from across the spectrum have appealed for calm.
The protesters, mainly from rural and small-town France, accuse Macron of favouring the rich and city-dwellers with his policies. Many are calling on him to resign.
Castaner on Friday estimated the number of people still taking part in demonstrations at 10,000 nationwide.
"10,000 is not the people, it's not France," he argued, despite polls showing them enjoying strong support.
Macron's "cardinal sin", in the eyes of the protesters, was to slash wealth taxes shortly after taking office, while hiking taxes on pensioners and cutting housing benefits.
The 40-year-old former investment banker has so far ruled out re-imposing the "fortune tax" on high-earners, arguing it is necessary to boost investment and create jobs.
But his climbdown on anti-pollution fuel taxes -- intended to help France transition to a greener economy -- marks a major departure for a leader who had prided himself on not giving into street protests.
Prime Minister Edouard Philippe signalled a willingness to make further concessions, saying the government was ready to consider "any measure which would allow us to boost spending power".
Macron himself has not commented publicly on the crisis since his return from the G20 summit in Argentina a week ago. He has signalled he will address the protests early next week.