SYDNEY (AFP) - An Australian newspaper on Saturday published a cartoon depicting the Prophet Muhammad arguing with Jesus, as it urged support for free speech in the wake of the deadly attack on a French satirical weekly.

Twelve people were killed in Wednesday's attack by extremists on magazine Charlie Hebdo'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 Mr Bill Leak entitled "Let us pray", in which Jesus is holding up the Quran and telling Muhammad: "I've told you this needs a sequel", a reference to the Bible which has an Old and New Testament.

To which Muhammad, 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, such as the cartoons published by Charlie Hebdo, are banned in Islam and mocking him angers many Muslims.

In an editorial, The Weekend Australian 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, Mr Leak said that by targetting a humorous magazine, the extremists had deliberately chosen "a symbol of the freedom of speech that lies at the very foundation of Western civilisation".

"A fine sense of humour is one of the defining characteristics of highly evolved, civilised human beings. Its absence is one of the defining characteristics of barbarism," he said.