The United States and Britain are promising to maintain a united front against Islamist extremists after militants killed 17 people in three days of attacks last week in Paris.
U.S. President Barack Obama and British Prime Minister David Cameron made the pledge as President Francois Hollande said Muslims are "the main victims of fanaticism, fundamentalism, and intolerance."
In a joint opinion article in the January 15 edition of The Times of London ahead of two days of meetings in Washington, Obama and Cameron said the world responded with "one voice" to the Paris attacks and that they would not allow anyone to "muzzle free speech."
"Whether we are facing lone fanatics or terrorist organizations, we will not be cowed by extremists," the leaders said. "We will defeat these barbaric killers and their distorted ideology."
In Berlin, German Chancellor Angela Merkel pledged to heighten security measures against Islamist extremists.
Speaking to parliament after a minute's silence for the victims of the Paris attacks, Merkel said, "Hate preachers, violent delinquents who act in the name of Islam, those behind them, and the intellectual arsonists of international terrorism will be rigorously fought with all legal means at the disposal of the state."
Two gunmen shouting Islamist slogans stormed into the headquarters of the satirical French weekly Charlie Hebdo on January 7, killing 12 people including senior editors and cartoonists.
The Yemen-based Al-Qaeda in the Arabian Peninsula claimed responsibility for the attack, saying the assailants, brothers Said and Cherif Kouachi, were assigned to attack the magazine as "vengeance" for the Prophet Muhammad.
The magazine had received repeated threats for its published caricatures of the Muslim Prophet.
Four Jewish men were killed on January 9 when a third gunman, Amedy Coulibaly, took hostages at a kosher supermarket in Paris.
Coulibaly and the Kouachi brothers were killed by security forces in near-simultaneous operations the same day.
In a speech at the Arab World Institute in Paris on January 15, Hollande said radical Islam had fed off poverty, inequality, and conflict, insisting that Islam is compatible with democracy.
He said any anti-Muslim or anti-Semitic acts must be "severely punished" as he sought to calm rising religious tensions.
"French Muslims have the same rights as all other French," Hollande said. "We have the obligation to protect them."
The president also thanked Arabs in France for their solidarity over the attacks.
Millions of people marched in Paris on January 11 to honor the victims, and the remaining staff of Charlie Hebdo quickly went to work on a new issue, which went on sale at newspaper kiosks across France on January 14.
After the new edition sold out in hours, Hollande said, "You can murder men and women but you can never kill their ideas."
"Charlie Hebdo is alive and will live on," he added.
The special edition will have a print run of 5 million issues, dwarfing the normal circulation of about 60,000.
It is available in six languages, including English, Arabic, and Turkish.
Proceeds are going to victims' families.
The new edition has drawn angry reactions in the Muslim world by depicting the Prophet Muhammad.
Its cover shows a cartoon featuring him shedding a tear and holding a sign reading "I Am Charlie" -- words that have been used by media outlets and millions of people worldwide to show solidarity with the victims and declare their support for freedom of speech.
In a resolution unanimously adopted on January 15, Pakistan’s lower parliament house, the National Assembly, condemned the cartoon and urged the international community, including the European Union, "to make sure such things are not repeated."
Some 50 lawmakers led by Minister for Religious Affairs Sardar Muhammad Yusaf later marched in front of the parliament building.
Several Islamic groups in the country are planning protest marches on January 16 against the publication of the cartoon.
In Ankara, Turkish Prime Minister Ahmet Davutoglu called the cartoon a "grave provocation" and added, "Freedom of the press does not mean freedom to insult" the Muslim Prophet.
"We are determined to protect the honor of the Prophet the same way as we are determined in our stance against terrorism in Paris," he told reporters.
Turkish opposition daily Cumhuriyet was reportedly the sole print publication in a majority Muslim country to reproduce cartoons and articles from Charlie Hebdo’s latest edition. But it stopped short of publishing the cover.
A Turkish court has ordered a block on access to Internet sites featuring the cover.
Iran had said the publication of the new Muhammad cartoon was "insulting" and "provocative."
The Palestinian militant group Hamas also denounced the cartoon, with senior leader Izzat Risheq saying it "poured oil on the fire."
The Afghan Taliban lauded the Charlie Hebdo attack, calling the publication of cartoons depicting the Prophet Muhammad an “obscene act.”
The Islamic State militant group said it was "an extremely stupid act."
The supermarket gunman, Coulibaly, had pledged allegiance to the group.
Meanwhile, a lawyer for Said Kouachi's wife, Soumya, told the BBC she had no idea he was an extremist.
The lawyer, Antoine Flasaquier, said Kouachi had kissed his wife goodbye and told her he was visiting his brother, just hours before the Charlie Hebdo attack.
French prosecutors have opened more than 50 cases against people accused of condoning terrorism or making threats to carry out terrorist acts.
U.S. Secretary of State John Kerry is due to meet Hollande in Paris on January 16 to discuss last week’s attacks.
Speaking in Bulgaria, Kerry said his visit to France “is basically to share a big hug for Paris and express our affection for France.”
With reporting by the Times, AFP, Reuters, and the BBC