FRANCE will close its embassies and schools in around 20 countries on Friday because of fears of a hostile reaction to a magazine's publication of cartoons of the Prophet Mohammed, the foreign ministry said.
Foreign Minister Laurent Fabius earlier announced that he had ordered special security measures "in all the countries where this could pose a problem."
Demonstrations in the Islamic world often follow Friday prayers.
Fabius admitted that he was "concerned" by the potential for a backlash to satirical weekly Charlie Hebdo's printing of a series of cartoons featuring the Prophet Mohammed against a background of violent protests in the Muslim world over an anti-Islam film.
The crudely-made US film is the main subject of Charlie Hebdo's cartoons but the sketches are open to wide interpretation.
The weekly carries a total of four cartoons.
The cover of Charlie Hebdo shows a Muslim in a wheelchair being pushed by an Orthodox Jew under the title "Intouchables 2", referring to an award-winning French film about a poor black man who helps an aristocratic quadriplegic.
Another cartoon on the back page of the weekly magazine shows the prophet re-enacting a scene from a Brigitte Bardot movie.
Charlie Hebdo's website crashed on Wednesday after being bombarded with comments that ranged from hate mail to approbation.
The magazine's editor, originally a cartoonist who uses the name Charb, denied he was being deliberately provocative at a delicate time.
"The freedom of the press, is that a provocation?" he said. "I'm not asking strict Muslims to read Charlie Hebdo, just like I wouldn't go to a mosque to listen to speeches that go against everything I believe."
Dalil Boubakeur, the senior cleric at Paris's biggest mosque, appealed for France's four million Muslims to remain calm.
"It is with astonishment, sadness and concern that I have learned that this publication is risking increasing the current outrage across the Muslim world," he said.
"I would appeal to them not to pour oil on the fire."
French Prime Minister Jean-Marc Ayrault said anyone offended by cartoons could take the matter to the courts after expressing his "disapproval of all excesses".
But he emphasised France's tradition of free speech. "We are in a country where freedom of expression is guaranteed, including the freedom to caricature," he said on RTL radio.
"If people really feel offended in their beliefs and think there has been an infringement of the law – and we are in a state where laws must be totally respected – they can go to court," Ayrault said.