LOS ANGELES, CA (Catholic Online) - France also faces a major problem on how to manage the country's four-million strong Muslim community, which French authorities have struggled to integrate in the past.

Security had been strengthened at institutions abroad and in France, with reinforcements and armed guards on standby. The French Foreign Ministry has issued a travel warning urging French citizens in the Muslim world to exercise "the greatest vigilance," and to avoid public gatherings and "sensitive buildings."

Protests stemming from the cartoons have already begun in Tehran and Kabul. Demonstrators chanted "death to France" outside the French embassies in the two capitals.

French schools were shut down in Tunisia until next Monday. "It's better not to take any chances, given that we don't really have faith in the security system," a parent outside a French school told TV reporters. "I don't understand the need to close for several days," he said.

Islamist militant Mu'awiyya al-Qahtani, called for reprisals in France as revenge for the cartoons. "Is there someone who will roll up his sleeves and bring back to us the glory of the hero Mohammed Merah?" he asked on an Islamist Internet forum. The post was in reference to an al Qaeda-inspired gunman who killed seven people, including three Jewish children, in the southern French city of Toulouse last March.

Interior Minister Manuel Valls banned all protests over the U.S.-produced video "Innocence of Muslims" following a violent demonstration last weekend near the U.S. embassy in Paris. Valls has made it clear he will not sanction any mass protests over the Charlie Hebdo cartoons, either.

Riot police have been deployed to protect Charlie Hebdo's offices, which were fire-bombed last year following the publication of an edition it said had been "guest edited" by the Prophet Mohammed that they dubbed "Sharia Hebdo."

Muslims are against the artistic representation of the prophet because they say it will inspire idolatry.

Charlie Hebdo's weekly editor, Stéphane Charbonnier, has also been assigned police body guards. He remains unfazed about the furor he has caused and has dismissed suggestions that his timing could have been better.

"The global circumstances will never be favorable to having a laugh at the expense of radical Islam or religion in general," he said. "If we take circumstances into account, we will not be able to talk about anything anymore - the satirical press is doomed."

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