The French government stepped up security Wednesday at its embassies across the Muslim world after a French satirical weekly published vulgar caricatures of the Prophet Muhammad on Wednesday, inflaming global tensions over a movie insulting to Islam.

The move by the provocative weekly Charlie Hebdo followed days of violent protests from Asia to Africa against the U.S.-produced film Innocence of Muslims and turned France into a potential target of Muslim rage. Up to now, American government sites have drawn the most ire.

Violence linked to the amateurish movie, which portrays the prophet as a fraud, a womanizer and a child molester, has killed at least 30 people in seven countries, including the American ambassador to Libya.

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A riot policeman stands guard outside the French embassy in Cairo on Wednesday, after a French magazine ridiculed the Prophet Muhammad by portraying him in cartoons. (Amr Abdallah Dalsh/Reuters)

The French government ordered embassies and schools abroad to close on Friday, the Muslim holy day, as a precautionary measure in about 20 countries, according to the foreign affairs ministry. It ordered the immediate closure of the French Embassy and the French school in Tunisia, which saw deadly film-related protests at the U.S. Embassy last Friday.

The French Foreign Ministry issued a travel warning Wednesday urging French citizens in the Muslim world to exercise "the greatest vigilance," avoiding public gatherings and "sensitive buildings" such as those representing the West or religious sites.

Cartoons ridiculed reaction to U.S. film

At the same time, the country — which has western Europe's largest Muslim population — plunged into a new debate over the limits of free speech in a modern democracy.

The principle of freedom of expression "must not be infringed," Foreign Minister Laurent Fabius said, speaking on France Inter radio.

But he added: "Is it pertinent, intelligent, in this context to pour oil on the fire? The answer is no."

France's prime minister said freedom of expression is guaranteed, but cautioned that it "should be exercised with responsibility and respect."

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The magazine's crude cartoons played off the film and ridiculed the violent reaction to it. Riot police took up positions outside the offices of the magazine, which was firebombed last year after it released an edition that mocked radical Islam.

Charlie Hebdo's chief editor, who goes by the name of Charb and has been under police protection for a year, defended the cartoons.

"Muhammad isn't sacred to me," he said in an interview at the weekly's offices on the northeast edge of Paris. "I don't blame Muslims for not laughing at our drawings. I live under French law; I don't live under Quranic law."

'I don't blame Muslims for not laughing at our drawings. I live under French law; I don't live under Quranic law.'—Charb, Charlie Hebdo magazine's chief editor

Charb said he had no regrets and felt no responsibility for any violence.

"I'm not the one going into the streets with stones and Kalashnikovs," he said. "We've had 1,000 issues and only three problems, all after front pages about radical Islam."

Government authorities and Muslim leaders urged calm.

"This is a disgraceful and hateful, useless and stupid provocation," Dalil Boubakeur, rector of the Grand Paris Mosque, told The Associated Press. "We are not Pavlov's animals to react at each insult."

A small-circulation weekly, Charlie Hebdo often draws attention for ridiculing sensitivity around the Prophet Muhammad, and an investigation into the firebombing of its offices last year is still open.

A lawsuit was filed against Charlie Hebdo hours after the issue hit newsstands, the Paris prosecutor's office said, though it would not say who filed it. The magazine also said its website had been hacked.

Abdallah Zekri, president of the Paris-based Anti-Islamophobia Observatory, said his group is considering filing a lawsuit against the magazine.

"People want to create trouble in France," he said. "Charlie Hebdo wants to make money on the backs of Muslims."

Charlie Hebdo was acquitted in 2008 by a Paris appeals court of "publicly abusing a group of people because of their religion" following a complaint by Muslim associations.

Prime Minister Jean-Marc Ayrault said organizers of a demonstration planned for Saturday against the Innocence of Muslims won't receive police authorization. Paris prosecutors have opened an investigation into an unauthorized protest last Saturday around the U.S. Embassy that drew about 150 people and led to scores of arrests.

The debate about the limits of free speech spread to neighbouring Germany, where Foreign Minister Guido Westerwelle spoke on the topic.

"I call on all those, especially those who rightly invoke the right of freedom of speech, to also act responsibly. The one who now puts more oil on the fire on purpose, with obvious effect, is not the greatest thinker," he said Wednesday in Berlin.

The German Embassy in Sudan, which was attacked last week, remains closed and security at German embassies in other countries has been beefed up, he said.

A German group in Berlin said it has dropped plans to show extracts of the film "Innocence of Muslims" because of the outcry it has caused.

The cartoonist of the French caricatures published Wednesday, who goes by the name Luz, was defiant.

"We treat the news like journalists. Some use cameras, some use computers. For us, it's a paper and pencil," he said. "A pencil is not a weapon. It's just a means of expression."

Outside the Charlie Hebdo offices, a passer-by wearing a traditional Muslim tunic said he was neither surprised nor shocked by the cartoons. He criticized France's decision to close embassies and schools for fear of protests by extremists.

"It gives legitimacy to movements that don't have any," said Hatim Essoufaly, who was walking his toddler in a stroller.