Pope Francis defended freedom of expression Thursday following the attack on a French satirical magazine deemed to have mocked the Prophet Muhammad — but added that it was wrong to provoke others by insulting their religion, and that one could "expect" a reaction to such provocation.

"You can't provoke, you can't insult the faith of others, you can't make fun of faith," he told reporters aboard a plane from Sri Lanka to the Philippines — where 80 percent of the population practice Roman Catholicism — on the second leg of his Asian tour.

Francis, who has condemned the Paris attacks, was asked about the relationship between freedom of religion and freedom of expression.

"I think both freedom of religion and freedom of expression are both fundamental human rights," he said, adding that he was talking specifically about the Paris killings.

"Everyone has not only the freedom and the right but the obligation to say what he thinks for the common good,” Francis said. “We have the right to have this freedom openly without offending."

To emphasize his point, he turned to an aide and said: "It is true that you must not react violently, but although we are good friends if (he) says a curse word against my mother, he can expect a punch, it's normal."

"You can't make a toy out of the religions of others," he added. “These people provoke and then [something can happen]. In freedom of expression there are limits."

The attack last week at the satirical weekly Charlie Hebdo left 12 people dead, after French authorities said brothers Said and Cherif Kouachi went on a shooting rampage at the publication’s offices in Paris. A total of 17 people, including journalists and police, were killed in three days of violence that began with the assault at Charlie Hebdo, which is known for its satirical attacks on Islam and other religions.

The paper had been repeatedly threatened over its caricatures of Muhammad — and was firebombed in 2011. Muslims believe their faith forbids any physical depiction of the prophet. The publication's first edition since the attacks, which featured a cartoon of Muhammad on the cover on the 5 million copies printed, sold out before dawn Thursday in Paris for a second straight day.

The Vatican and four prominent French imams recently issued a joint declaration that denounced the attacks but urged the media to treat religions with respect.

Francis, who has urged Muslim leaders in particular to speak out against extremism, went a step further when asked by a French journalist about whether there should be limits when freedom of expression meets freedom of religion.

Referring to past religious wars, such as the Crusades sanctioned by the Roman Catholic Church against Islam, the pope said, "Let's consider our own history. How many wars of religion have we had? Even we were sinners, but you can't kill in the name of God. That is an aberration."

Francis was also asked if he felt vulnerable to an assassination attempt or other attack by extremists. Earlier this week, the Vatican denied Italian media reports that U.S. and Israeli intelligence officials had informed the Vatican that there could be an imminent attack.

Francis said that he was more worried about others being hurt in an eventual attack, and that he was confident about security measures in the Vatican and during his trips.

"I am in God's hands," he said, joking about having asked God to spare him a painful death.

"Am I afraid? You know that I have a defect, a nice dose of being careless. If anything should happen to me, I have told the Lord, I ask you only to give me the grace that it doesn't hurt because I am not courageous when confronted with pain. I am very timid," he said.

Al Jazeera and wire services