France has ordered prosecutors around the country to crack down on hate speech, anti-Semitism and glorifying terrorism and is sending an aircraft carrier to the Middle East to work more closely with the US-led coalition fighting Islamic State militants.
Authorities said 54 people had been arrested for hate speech and defending terrorism in the last week.
The crackdown came as Charlie Hebdo's defiant new issue sold out before dawn around Paris, with scuffles at kiosks over dwindling copies of the satirical weekly that depicted the Prophet Mohammed anew on its cover.
After terror attacks killed 20 people in Paris last week, including three gunmen, President Francois Hollande said the situation "justifies the presence of our aircraft carrier". One of the gunmen claimed allegiance to IS.
France is already carrying out air strikes against the extremist group in Iraq. Mr Hollande spoke aboard the Charles de Gaulle aircraft carrier to members of France's military.
Since the attacks, France has deployed 10,000 troops and 120,000 security forces to protect sensitive sites, including Jewish schools and synagogues, mosques and travel hubs.
France has been tightening security and searching for accomplices since the terror attacks began, but none of the 54 people mentioned have been linked to the attacks.
That is raising questions about whether Mr Hollande's Socialist government is impinging on the very freedom of speech that it so vigorously defends when it comes to Charlie Hebdo.
Among those detained was Dieudonne, a popular and controversial comedian who has repeated convictions for racism and anti-Semitism.
Like many European countries, France has strong laws against hate speech, especially anti-Semitism in the wake of the Holocaust.
In a message distributed to all French prosecutors and judges, the justice ministry laid out the legal basis for rounding up those who defend the Paris terror attacks as well as those responsible for racist or anti-Semitic words or acts. The order did not mention Islam.
A top leader of Yemen's al Qaida branch claimed responsibility for the Charlie Hebdo attack, saying in a video the massacre came in "vengeance for the prophet". The newspaper had received repeated threats previously for posting caricatures of Mohammed.
The core of the irreverent newspaper's staff died a week ago when gunmen stormed its offices, killing 12 people and igniting three days of bloodshed around Paris that left 17 victims dead. The attacks ended on Friday when security forces killed both gunmen and an accomplice who separately seized hostages at a kosher grocery.
Working out of borrowed offices, Charlie Hebdo employees who survived put out the issue that appeared today with a print run of three million - more than 50 times the paper's usual circulation. After the weekly sold out, kiosk operators told people to return tomorrow for a second run.
French police say as many as six members of the terror cell may still be at large, including a man seen driving a car registered to the widow of one of the gunmen. Officials say the widow is now in Syria. There has been no word on the whereabouts of the driver or the car.
The justice ministry said the 54 people included four minors and several had already been convicted under special measures for immediate sentencing. Inciting terrorism can bring a five-year prison term - or up to seven years for inciting terrorism online.
In its message to prosecutors and judges, the ministry said it was issuing the order to protect freedom of expression from comments that could incite violence or hatred. It said no one should be allowed to use their religion to justify hate speech.
"We have all heard 'Yes, I support Charlie, but,' the double standards, the 'Why defend liberty of expression here and not there?'" education minister Najat Vallaud Belkacem said. "These questions are intolerable above all when we hear them at school, which has the duty to teach our values."
The government order warned authorities to be particularly attentive to any incidents that could lead to urban unrest or violence against police. That suggested the government fears new riots like the wave that swept through France's neglected housing projects and immigrant communities a decade ago.
The government is writing broader new laws on phone-tapping and other intelligence to fight terrorism, spokesman Stephane Le Foll said. It is also launching a deeper project to rethink France's education system, urban policies and integration model in an apparent recognition that last week's attacks exposed deeper problems about inequality in France, especially at its housing projects.
Dieudonne, a comedian who popularised an arm gesture that resembles a Nazi salute and who has been convicted repeatedly of racism and anti-Semitism, is no stranger to controversy. His provocative performances were banned last year but he has a core following among France's disaffected youth.
In a Facebook post that was swiftly deleted, the comic said he felt like "Charlie Coulibaly" - merging the names of Charlie Hebdo and Amedy Coulibaly, the gunman who killed four hostages at a kosher market on Friday, a day after he killed a Paris policewoman.
In a separate post, the comedian wrote an open letter to France's interior minister.
"Whenever I speak, you do not try to understand what I'm trying to say, you do not want to listen to me. You are looking for a pretext to forbid me. You consider me like Amedy Coulibaly when I am not any different from Charlie," he wrote.
Coulibaly had claimed allegiance to IS while Said and Cherif Kouachi, the two brothers behind the Charlie Hebdo massacre, had told survivors they were sent by al Qaida in Yemen.
In an 11-minute video, Nasr Ansi, a top commander of Al Qaida in the Arabian Peninsula, or AQAP, said Yemen's al Qaida branch "chose the target, laid out the plan and financed the operation".
US intelligence officials, however, said they have no evidence AQAP co0ordinated the attack or knew about it in advance.
Solidarity for Charlie Hebdo, although not uniform, was widespread in France and abroad and the new issue vanished from kiosks immediately. One newsstand near the Champs Elysees opened at 6am and was sold out in five minutes. Another, near Saint-Lazare, reported fisticuffs among customers.
Defending his caricature of Mohammed on the paper's latest cover, Charlie Hebdo cartoonist Renald Luzier argued that no exceptions should be made when it comes to the freedom of expression.
He said when the weekly was threatened in the past, the reaction was often: "Yes, but you shouldn't do that (publish cartoons of Mohammed). Yes, but you deserved that."
"There should be no more 'Yes, but'," he insisted.
French interior minister Bernard Cazeneuve was among those getting a copy before they sold out.
"I rediscovered their liberty of tone," he told France-Inter radio.
French prime minister Manuel Valls displayed a copy of the satirical paper as he left a cabinet meeting but his hand carefully covered Mohammed's face.