Politicians and Muslim leaders have denounced a firebomb attack that destroyed the offices of a satirical French newspaper after it "invited" the Prophet Mohammed as its guest editor.
No one was injured in the fire at Charlie Hebdo weekly in eastern Paris, hours before the current issue hit the news-stands.
"Everything will be done to find those behind this attack," said Interior Minister Claude Gueant.
One witness saw someone throwing two firebombs at the building and the newspaper's director, who goes by the name Charb, said a Molotov cocktail was the cause of the fire. He blamed "radical stupid people who don't know what Islam is," for the apparent attack.
"I think that they are themselves unbelievers ... idiots who betray their own religion," he said.
The front-page of the weekly, subtitled "Sharia Hebdo," a reference to Islamic law, showed a cartoon-like man with a turban, white robe and beard smiling broadly and saying, in an accompanying bubble, "100 lashes if you don't die laughing."
Previous depictions of the prophet have caused major disturbances in Muslim countries. Islamic law generally opposes any depiction of the prophet, even favourable, for fear it could lead to idolatry.
Ever since Danish newspaper Jyllands-Posten published a dozen cartoons of Mohammed in 2005, police have foiled a series of terror plots against it and cartoonist Kurt Westergaard, who drew one of the most controversial caricatures depicting Mohammed wearing a turban shaped like a bomb with a lit fuse.
Charlie Hebdo had also reproduced the cartoons, that led to a complaint by Muslim associations. The weekly was acquitted in 2008 by a Paris appeals court of "publicly abusing a group of people because of their religion."
France's Prime Minister Francois Fillon called on officials to move quickly to find those responsible and bring them to justice.
"Freedom of expression is an inalienable value of our democracy .... No cause can justify a violent action," he said. A handful of ministers echoed similar indignation.
Leading Muslim figures in France, a country that has western Europe's largest Muslim population, estimated at five million, also condemned the attack.
Mohammed Moussaoui, head of the French Council for the Muslim Faith, said his organisation deplored "the very mocking tone of the paper toward Islam and its prophet but reaffirms with force its total opposition to all acts and all forms of violence."
Dalil Boubakeur, who heads the Great Mosque of Paris, condemned "an act which can in no way represent the principles of liberty, tolerance and peace that are (our) message." But he regretted the "anxious European climate of Islamophobia" fed in part by stigmatising Muslims through caricatures.
The current issue was centred on last week's victory of a once-banned Islamist party in Tunisia's first free elections and last month decision by Libya's new leaders that Sharia, or Islamic legislation, will be the main source of law in post-Gaddafi Libya.
"It was a joke where the topic was to imagine a world where Sharia would be applied," Charb said. "But since everyone tells us not to worry about Libya or Tunisia, we wanted to explain what would be a soft version of Sharia, a Sharia applied in a soft manner."
He vowed to continue publishing the weekly and Paris Mayor Bertrand Delanoe said the city would help find a new office space.
Newspaper employees said they had received numerous threats and insults via social networks as a result of this week's publication. The newspaper's website was hacked for several hours and visitors were directed to an Islamist website.