PARIS - Gunmen behind the attack on satirical magazine Charlie Hebdo reportedly yelled, "We have avenged the Prophet!" as they stormed the office.
The weekly magazine has a controversial history of depicting Prophet Muhammad, often in an unfavourable light, which has angered many Muslims around the world.
In 2012, when Charlie Hebdo editors defied the government's advice and published crude caricatures of the Prophet Muhammad naked and in sexual poses, the French authorities shut down embassies, cultural centres and schools in about 20 countries.
Mr Jean-Marc Ayrault, France's then Prime Minister, defended the magazines right to publish but openly asked whether it had been acting responsibly.
For many Muslims, satirical depictions of Prophet Muhammad, revered not only as a prophet but also as a moral exemplar, are no laughing matter.
Islamic scholar Moataz al-Khateeb explains that all the prophets - Muhammad, Jesus, Moses and others (of the Abrahamic religions) - are highly respected figures in the Islamic faith. One cannot differentiate between them in terms of the reverence that should be given to each.
"Therefore Muslims believe that the prophets have a higher status than other people. To ridicule them or their lives is an insult to the origin of their faith, and therefore any abuse to them is abuse of Muslims in general," he told the Al Jazeera website.
Mr Mohamed Magid, an imam and former head of Islamic Society of North America, told CNN the Muslim prohibition on depicting prophets extends to Jesus and Moses, whom Islam treats as prophets. Some Muslim countries banned the films Noah and Exodus: Gods And Kings this year because their leading characters were Hebrew prophets.
Scholars of religion say Muslim opposition to portraying the Prophet wasn't generally violated in earlier centuries because of a gulf between much of the Muslim world and the West, reported the CNN in a piece titled "Why Islam forbids images of Mohammed" and written by its religion editor Daniel Burke.
In the age of globalisation, non-Muslims and critics of Islam have felt free to depict Prophet Muhammad, including in offensive ways but publication in Europe of these cartoons have triggered protests worldwide.
Commentators and Islamic scholars say the prohibition against any depiction of Prophet Muhammad is an attempt to ward off idol worship, which used to be widespread in Islam's Arabian birthplace.
A central tenet of Islam is that Prophet Muhammad was a man, not God, and that portraying him could lead to revering a human in lieu of Allah.
"It's all rooted in the notion of idol worship," says Mr Akbar Ahmed, who chairs the Islamic Studies department at American University.
"In Islam, the notion of God versus any depiction of God or any sacred figure is very strong," he told CNN.
"The Prophet himself was aware that if people saw his face portrayed by people, they would soon start worshipping him," Mr Ahmed says. "So he himself spoke against such images, saying 'I'm just a man.' "
In the 15th and 16th centuries, Muslim artists would depict the Prophet but took pains to avoid drawing his face. In the film called The Messenger, which circulated throughout the Muslim world in the 1970s and 1980s, the Prophet was depicted only as a shadow.
The most common visual representation of the Prophet Muhammad in Islamic art is by elaborate swirling Arabic calligraphy, wrote The Guardian's Middle East editor Ian Black.
The Taleban's destruction of statues of Buddha in Kandahar in Afghanistan is a notorious example of the intolerance of images, part of the school of tawhid - usually translated as Islamic monotheism, he wrote on The Guardian website.
"Sunni disapproval of Shia Muslim shrines reflects this too. Shias are more flexible than Sunnis and display images of Husayn, the grandson of Muhammad," wrote Mr Black.
Professor Hussein Rashid, a professor of Islamic studies at Hofstra University in New York, said the outrage was more than just religious anger.
"In the context of Europe, where in many countries Muslims feel like they are besieged, these images are not seen as criticism, but as bullying. Violence, as a response, is clearly wrong and disproportionate. However, it is not so much about religious anger, as it is about vengeance," he was quoted as saying by CNN.