Pope Francis has defended freedom of expression following last week's attack on French satirical magazine Charlie Hebdo - but also stressed its limits.
The pontiff said religions had to be treated with respect, so that people's faiths were not insulted or ridiculed.
To illustrate his point, he told journalists that his assistant could expect a punch if he cursed his mother.
The remarks came as funerals were held for four people killed in the attack by militant Islamists.
Friends and family paid last respects to cartoonists Bernard Verlhac, known as Tignous, and Georges Wolinski, as well as columnist Elsa Cayat and policeman Franck Brinsolaro.
Eight magazine staff, a visitor to the magazine, a caretaker and two policemen died in the attack. A policewoman and four people at a kosher supermarket died in separate attacks.
Al-Qaeda said it had directed the Charlie Hebdo attack.
The magazine was targeted for publishing cartoons of the Prophet Muhammad. It printed another cartoon of the Prophet on its front page after the attacks, angering some Muslims who say all depictions of the Prophet should be forbidden.
France has deployed thousands of troops and police to boost security in the wake of last week's attacks. There have been retaliatory attacks against Muslim sites around France.
Meanwhile the creator of the "Je suis Charlie" slogan, which became a symbol of support for Charlie Hebdo, has applied for a patent, saying that he wants to prevent the commercial exploitation of the design and keep its original message intact.
'You cannot provoke'
Speaking to journalists flying with him to the Philippines, Pope Francis said last week's attacks were an "aberration", and such horrific violence in God's name could not be justified.
He staunchly defended freedom of expression, but then he said there were limits, especially when people mocked religion.
"If my good friend Doctor Gasparri [who organises the Pope's trips] speaks badly of my mother, he can expect to get punched," he said, throwing a pretend punch at the doctor, who was standing beside him.
"You cannot provoke. You cannot insult the faith of others. You cannot make fun of the faith of others. There is a limit."
Earlier President Francois Hollande vowed to protect Muslims who, he said, were the main victims of fanaticism, along with people of other religions.
Speaking at the Arab World Institute, he said anti-Muslim and anti-Semitic acts should be condemned and punished.
In a separate development, the government announced that a Malian employee of the Jewish supermarket that was attacked would be given French citizenship.
Some 300,000 people signed an online petition calling for the move after the Muslim employee, Lassana Bathily, hid several customers from the gunman in a cold store.
Charlie Hebdo published a new edition on Wednesday, with an image on the cover showing the Prophet Muhammad weeping while holding a sign saying "I am Charlie", and below the headline "All is forgiven".
Mr Hollande declared Charlie Hebdo magazine "reborn" after the magazine sold out in hours.
But some Muslims were angered by the edition and Turkish Prime Minister Ahmet Davutoglu condemned it on Thursday as an "open provocation".
In Pakistan on Thursday, lawmakers unanimously approved a resolution condemning the publication of the images, and several hundred demonstrators from a religious party called for cartoonists who drew pictures of the Prophet Muhammad to be hanged.
'Our magazine will live'
A private funeral service was held for cartoonist Tignous, 57, in the suburb of Montreuil, ahead of his burial in Pere Lachaise, Paris' best known resting place for writers, artists and composers.
A ceremony was held at Pere Lachaise for Wolinski, who was to be cremated.
Crowds in Montreuil applauded Tignous' coffin as it arrived for the ceremony at Montreuil town hall covered in drawings and messages from well-wishers.
In a tribute at the ceremony, Tignous' colleague Corinne Rey described him as the "king of jokes".
"Our magazine will live, it will be a different magazine," she said. "You were never afraid, my Titi and be assured, we won't be afraid either."
At Wolinski's funeral, his daughter Elsa said his ideals would live on.
"I'm beginning to realise that he is gone," she said. "But as I said before, they've killed a man and not his ideas. So here we are. We stand here and will continue to defend the principles of Charlie Hebdo."
How the attacks unfolded (all times GMT)
- Wednesday 7 January 10:30 - Two masked gunmen enter Charlie Hebdo offices, killing 11 people, including the magazine's editor. Shortly after the attack, the gunmen kill a police officer nearby.
- 11:00 - Police lose track of the men after they abandon their getaway car and hijack another vehicle. They are later identified as brothers Said and Cherif Kouachi.
- Thursday 8 January 08:45 - A lone gunman shoots dead a policewoman and injures a man in the south of Paris. Gunman later identified as Amedy Coulibaly.
- 10:30 - The Kouachi brothers rob a service station near Villers-Cotterets, in the Aisne region, but disappear again.
- Friday 9 January 08:30 - Police exchange gunfire with the Kouachi brothers during a car chase on the National 2 highway northeast of Paris.
- 10:00 - Police surround the brothers at an industrial building in at Dammartin-en-Goele, 35km (22 miles) from Paris.
- 12:15 - Coulibaly reappears and takes several people hostage at a kosher supermarket in eastern Paris. Heavily armed police arrive and surround the store.
- 16:00 - Kouachi brothers come out of the warehouse, firing at police. They are both shot dead.
- 16:15 - Police storm the kosher supermarket in Paris, killing Coulibaly and rescuing 15 hostages. The bodies of four hostages are recovered.