Anti-government protests in France have "created a monster," said French Interior Minister Christophe Castaner.
And warns that "radical elements" could infiltrate the planned "yellow vests" protests over the weekend.
Saturday the tourist sites of Paris close between fears of further street violence.
The protests began three weeks ago, initially against an increase in fuel taxes, but spread to other issues, including education reforms.
Mr. Castaner said that "large-scale security measures" will be implemented this weekend.
Throughout France, 89,000 policemen will be on duty and armored vehicles will be deployed in the capital, announced Prime Minister Edouard Philippe.
The Paris police have pushed shops and restaurants on the Champs-Elysees to close and some museums will be closed.
The government said it is demolishing the unpopular increases in fuel taxes in its budget – but the discontent with the government has spread and protests have erupted on other issues
Further protests have been reported in the east of the country.
A student was injured as a result of a demonstration in the city of Montbéliard, about 13 km from the border with Switzerland, local media report. A policeman was seriously injured in a student protest in Mulhouse, according to the French broadcaster BFMTV.
The AFP news agency reports that the authorities have seized 28 molotovs and 3 homemade bombs from protesters of the "yellow jersey" in the south of the country.
There was also anger spread to images showing how the police knelt high school students and put their hands behind their heads after Thursday's clashes at Mantes-la-Jolie, west of Paris.
What did the government say?
Mr. Castaner told reporters that the last three weeks of demonstrations "created a monster escaped from its creators".
He said that the authorities would respond with "firmness".
He continued: "I will not tolerate those who capitalize the anguish of our citizens."
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- The ball in the court of Macron after violent protests
An official of the Ministry of the Interior stated that the authorities of the AFP press agency were reinforced by "significant violence" on Saturday, with the activists of the extreme right and the extreme left who want to converge on the capital.
In an interview with the TV channel TF1, Mr Philippe said that 8,000 policemen would be deployed in Paris and a dozen armored vehicles.
He repeated an appeal for calm, but added: "We are faced with people who are not here to protest, but to destroy and we want to have the means to not give them a free rein."
Earlier, Mr Philippe suggested that there may be further concessions to protesters, telling the Senate that the government was open to new measures to help higher paid workers.
How will Paris be affected?
The operator of the Eiffel Tower said the threat of violent Saturday protests made it impossible to ensure "adequate security conditions".
City authorities say they are stepping up the protection of famous monuments after the Arc de Triomphe was damaged last week.
The museums, including the Louvre and Orsay, the opera houses and the Grand Palais complex will close on Saturday
The police asked the companies of the Champs-Elysees and other important commercial streets to remain closed and to remove any open-air objects such as tables and chairs.
Several football matches have also been postponed, including those between Paris and Montpellier, and Saint-Etienne and Marseille.
What other protests were there?
Young people took to the streets on Thursday, protesting about educational reforms.
More than 140 people were arrested when a protest outside a school in Mantes-la-Jolie, west of Paris, ended in clashes with the police. Two cars were burned.
The images of the arrests, in which the students were forced to kneel and put their hands behind their heads, sparked outrage over social media. The French broadcaster BFMTV stated that the incident lasted "several hours".
"Now there is a well-behaved class", a police office was told in video.
The city police chief told the newspaper Le Monde that the arrested were suspected of taking part in an "armed gathering," adding that the agents wanted to break a situation that was becoming "out of control".
Education Minister Jean-Michel Blanquer said he was "clearly shocked" by the events, but added that they must be put in context. Mr Castaner described the images as "difficult" to observe, but added that the students had been joined by armed demonstrators.
Dozens of schools were blocked in cities such as Marseilles, Nantes and Paris. The students were irritated by President Emmanuel Macron's plans to change the end-of-school exam, known as the baccalaureate, which is required for entry to the university.
Critics fear that reforms limit opportunities and generate inequality.
Who are the demonstrators?
Protesters of the "gilets jaunes", so called because they took to the streets wearing high visibility yellow clothing that is required to be transported in each vehicle by French law, initially complained of a sharp increase in taxes on the diesel.
Macron said his motivation for the increase was environmental, but protesters accused him of being out of control.
The government then demolished the plan, but the yellow jacket protesters were not appeased. Last week, the movement – despite the lack of a central leadership – released more than 40 requests to the government
Among these were a minimum pension, widespread changes to the tax system and a reduction in the age retirement.
The protest movement gained momentum through social media, including a whole range of participants from the anarchist left to the far right nationalist, and moderate in the middle.