The Weekend Australian today published a cartoon depicting the Prophet Mohammed arguing with Jesus, as it urged support for free speech in the wake of the deadly attack on staff at the French satirical magazine Charlie Hebdo .

Twelve people were killed in Wednesday's attack by extremists on the magazine's office in Paris, prompting cartoonists around the world to put pen to paper in solidarity with their French colleagues.

The Weekend Australian newspaper published the cartoon by Bill Leak entitled "Let us pray" in which Jesus is holding up the Koran and telling Mohammed: "I've told you this needs a sequel", a reference to the Bible which has an Old and New Testament.

To which Mohammed, brandishing a newspaper with the headline "World at War", replies he can't return to human form right now because he would be "crucified".

Depictions of the Prophet Mohammed such as the cartoons published by Charlie Hebdo are banned in Islam and mocking him angers many Muslims.

In an editorial, the newspaper called on the Western world to show no weakness in defending its core values or retreat from free speech.

"Whether deliberate or not, one of the most damaging aspects of this atrocity," it said of the Paris attack, "is that it hit our civilisation in a place already shaping as our Achilles Heel - a spineless and growing penchant for political correctness.

"Over recent years, in the face of the perpetually outraged, our pluralistic, democratic and free societies have gradually been yielding on our hard-won freedom of expression," it said.

In an opinion piece on Friday, Leak said that by targeting a humorous magazine, the extremists had deliberately chosen "a symbol of the freedom of speech that lies at the very foundation of Western civilisation".