The French authorities moved on Wednesday to reinforce a clampdown on hate speech and anti-Semitism, as the weekly newspaper Charlie Hebdo returned defiantly to the newsstands with a depiction of the Prophet Mohammad on its cover, just one week after Islamist gunmen slaughtered 12 people in an attack on its offices.
In some places, vendors reported that their allotment of the publication had sold out before daybreak, and demand was so intense that copies of the newspaper were being offered on eBay for hundreds of dollars. Some vendors drew up waiting lists of customers in anticipation of new supplies for a print run that could reach five million, compared with 60,000 before the attacks.
The frenzy drew a vivid backdrop to the sharpening debate between proponents of press freedom and defenders of religious proprieties. The three-day onslaught last week has left the French authorities struggling to find ways to confront an unfamiliar form of terrorism, by lone militants or groups that are difficult to detect.
Thousands of troops and police officers have been deployed on the streets, but the authorities are also trying to move against what the prime minister, Manuel Valls, called social media sites that are "more than ever used for indoctrination" of militants who use the internet to communicate and acquire "techniques permitting them to act."
The interior minister, Bernard Cazeneuve, said on Wednesday that he would soon visit the United States, where he will try to persuade large American Internet companies to support counterterrorism action by governments.
At a meeting of interior ministers in Paris on Sunday, Cazeneuve told a French radio station that senior law enforcement officials, including Americans, were in favour of establishing "close contact with Twitter, Google and other operators to say to them: Look out, there is a problem. You must mobilise with us."
His remarks reflected an increasingly tense confrontation between governments seeking easier access to data as part of counterterrorism campaigns, and technology giants prepared to use increasing levels of encryption to avoid the perception that they act as agents of official intelligence-gathering.
In an official circular to prosecutors on Wednesday, meanwhile, the French Justice Ministry laid out plans for a crackdown on what it described as an increase in attacks against places of worship; abuse on the grounds of religion; violence or threats against security forces; racist, anti-Semitic or discriminatory speech; and the glorification of terrorism.
Prosecutors should guarantee "a systematic criminal response" to such offenses, especially those committed in prison, it said.
As part of the same broad response to the attacks, 54 people are under investigation related to charges of glorifying terrorism and terrorism threats, according to Pierre Rance, a spokesman for the Justice Ministry. Thirty-seven people are suspected of glorifying terrorism, with the rest described as people who have threatened to carry out terrorist acts.
The office of the Paris prosecutor, meanwhile, said separately on Wednesday that a highly provocative French comedian, Dieudonne M'bala M'bala, had been detained as an "apologist for terrorism" because of a comment on Facebook about one of the attackers in Paris.
Prosecutors opened an investigation into the comedian on Monday after he referred in a Facebook post to Amedy Coulibaly, accused of killing four hostages at a kosher supermarket in Paris on Friday and of fatally shooting a police officer the day before.
Mr. Coulibaly was shot to death by the police on Friday at almost the same time security forces killed Saïd and Cherif Kouachi, the brothers who are suspected in the Charlie Hebdo attacks, at a printing warehouse northeast of Paris.
©2015 The New York Times News Service