The offices of the French satirical magazine Charlie Hebdo in Paris have been destroyed in a petrol bomb attack.
It comes a day after the publication named the Prophet Muhammad as its "editor-in-chief" for its next issue.
The cover of the magazine carried a caricature of the Prophet making a facetious comment.
French Prime Minister Francois Fillon has described the petrol-bombing as an unjustifable attack on the freedom of the press.
The editor-in-chief of the magazine, Stephane Charbonnier, said Islam could not be excluded from freedom of the press.
He said: "If we can poke fun at everything in France, if we can talk about anything in France apart from Islam or the consequences of Islamism, that is annoying."
Mr Charbonnier, also known as Charb, said he did not see the attack on the magazine as the work of French Muslims, but of what he called "idiot extremists".
The magazine said Wednesday's edition was intended to "celebrate" the victory of an Islamist party in last month's Tunisian elections.
Charb said the magazine had received several threats on Twitter and Facebook before the attack.
"This is the first time we have been physically attacked, but we won't let it get to us," he said.
Police said Charlie Hebdo's headquarters had been petrol-bombed in the early hours of Wednesday morning.
There have been no reports of injuries.
Charlie Hebdo's website has also been hacked with a message in English and Turkish attacking the magazine.
The edition of the paper published on Wednesday was called Charia Hebdo - a play on the Islamic word sharia.
The cover shows Muhammad saying: "100 lashes if you are not dying of laughter".
Inside, there is an editorial, attributed to the Prophet Muhammad, and more cartoons - one showing the Prophet with a clown's red nose.
Depiction of the Prophet is strictly prohibited in Islam.
In a statement on Tuesday, the magazine said it was motivated by the recent victory of the Islamist Ennadha party in elections in Tunisia, and by indications that sharia law could form the basis of legislation in post-Gaddafi Libya.
The magazine denied it was trying to be provocative.
On Tuesday, Charb told the AFP news agency : "We don't feel like causing further provocation. We simply feel like doing our job as usual. The only difference this week is that Muhammad is on the cover and it's pretty rare to put him on the cover."
Prime Minister Fillon expressed his "indignation" at the attack on the newspaper.
"Freedom of expression is an inalienable right in our democracy and all attacks on the freedom of the press must be condemned with the greatest firmness. No cause can justify such an act of violence," he said in a statement.
The head of the French Council of the Muslim Faith, Mohammed Moussaoui, also condemned the attack.
In 2007, Charlie Hebdo reprinted 12 controversial cartoons of the Prophet Muhammad that were first shown in a Danish newspaper, Jyllands-Posten, and caused outrage in the Muslim world.
The magazine was sued for incitement to racism by two Islamic groups in France, but was acquitted by a Paris court.
The BBC's Paris correspondent Hugh Schofield says Charlie Hebdo has a long track record of irreverence to all religions.