Depictions of Prophet Mohammed such as the cartoons published by the French satirical magazine reeling from a deadly attack are banned in Islam and mocking him angers many Muslims.
Although images poking fun at the prophet have repeatedly infuriated the Islamic world, Arab and Muslim leaders and clerics were quick to condemn the attack. Sunni Islam's most prestigious centre of learning Al-Azhar said "Islam denounces any violence".
The two masked gunmen who killed 12 people at the Charlie Hebdo weekly on Wednesday claimed to be on a mission to "avenge" its cartoons of Mohammed.
It follows years of controversy over such caricatures.
"This is a prophet that is revered by some two billion people... Is it moral to mock him?," prominent Iraqi preacher Ahmed al-Kubaisi told AFP, explaining the violent reaction of Muslims to cartoons of Mohammed.
"France is the mother of all freedoms, yet no one said this (depiction) is shameful," he said.
Outspoken former Malaysian prime minister Mahathir Mohamad said Charlie Hebdo had shown disrespect towards Islam on numerous occasions.
"Is there a need for them to ridicule Prophet Mohammed knowing that they are offending Muslims?" state news agency Bernama quoted him as saying.
"We respect their religion and they must respect our religion," he added.
Violent protests broke out in the Muslim world after Denmark's Jyllands-Posten newspaper published 12 caricatures of Mohammed in 2005.
Charlie Hebdo and other European publications reproduced the cartoons the following year, including one which showed Mohammed wearing a turban shaped like a bomb, making them a target of Islamist fury.
The French magazine's offices were fire-bombed in November 2011 following the publication of an edition renamed "Charia Hebdo", (Sharia Hebdo), with a caricature of Mohammed on the front page.
- 'No respect for freedom' -
At the core of the problem is the "lack of respect for others' right to freedom of expression" in Arab and Muslim countries, according to Hassan Barari, professor of international relations at Qatar University.
Some people "do not understand the Western context of free speech, where you can easily make a movie that is critical of Jesus."
Mathieu Guidere, who teaches Islamic studies at France's University of Toulouse, said that the "culture of tolerance, and acceptance of different opinion is almost non-existent in the Arab and Islamic world."
He attributed violence to a feeling harboured by "almost every Muslim who believes that he is the defender of the prophet and of Islam."
Barari pointed to a history of "animosity between the West and Muslims".
"We cannot deny that anti-Western feeling in the region is related to the West's policies. This is related to past colonialism, policy on Israel, and support to dictatorships," he said.
- Even positive depiction banned -
The majority of Islamic scholars ban drawings of all prophets revered by Islam, and reject the depiction of the companions of Mohammed, even when it shows them in a positive light
"We should not open the door to people to draw the prophet in different forms that could affect his status in the hearts of his people," said Kubaisi, the Iraqi preacher who is based in Dubai
There is no text from the Quran or the tradition of the prophet that clearly forbids such depictions, and the ban is "out of homage and respect" to the prophets, he added.
The ban also applies to depictions of prophets and companions of Mohammed in movies and television programmes.
When a trailer for anti-Muslim movie "Innocence of Muslims" appeared on YouTube in 2012, protesters took to the streets in several countries.
Four people, including US Ambassador Chris Stevens, were killed in Libya when extremists used protests against the film to attack US interests on September 11, 2012.
In recent weeks, a number of Muslim countries banned Ridley Scott's "Exodus: Gods and Kings" for its depiction of Moses.
Even the 1970s epic "The Message", which chronicled the life of Mohammed and starred Anthony Quinn, did not impersonate the prophet.
"Depicting the prophets of Allah would cast doubts about their status and might include lies, because actors could never match the characters of the prophets," said a fatwa, or edict, by the Mecca-based Islamic Fiqh Council.