PARIS (CBSNewYork/AP) -- Millions of people marched through France on Sunday in a massive show of unity and defiance in the face of terrorism that killed 17 people in the country's bleakest moment in half a century.
Their arms linked, more than 40 world leaders headed the somber procession, setting aside their differences for a manifestation that French President Francois Hollande said turned the city into "the capital of the world.''
Israeli Prime Minister Benjamin Netanyahu stood near Palestinian President Mahmoud Abbas. Ukrainian President Petro Poroshenko and Russian Foreign Minister Sergey Lavrov also marched.
The French Interior Ministry said 3.7 million marched throughout France -- an estimated 2.5 million marched across France in cities and towns Sunday, and between 1.2 and 1.6 million in Paris. But it said a precise account is impossible given the enormity of the turnout in the capital.
Earlier, the ministry said it was an unprecedented turnout.
The deadly attacks on a satirical newspaper, kosher market and police marked a turning point for France that some compared to Sept. 11. In the weeks and months ahead, the cruelty will test how attached the French -- an estimated 5 million of whom are Muslims -- really are to their liberties and to each other.
"Our entire country will rise up toward something better," Hollande said Sunday.
The aftermath of the attacks remained raw, with video emerging of one of the gunmen killed during police raids pledging allegiance to the Islamic State group and detailing how the attacks were going to unfold. Also, a new shooting was linked to that gunman, Amedy Coulibaly, who was killed Friday along with the brothers behind the massacre at satirical newspaper Charlie Hebdo in nearly simultaneous raids by security forces.
Rallies were planned throughout France and major cities around the world, including London, Madrid and New York -- all attacked by al Qaeda-linked extremists -- as well as Cairo, Sydney, Stockholm, Tokyo and elsewhere.
Children, grandparents, Muslims, Jews, Christians, workers, bosses -- all joined together in streets and plazas thronged with crowds throughout eastern Paris.
On Paris' Republic Square, deafening applause rang out as the world leaders walked past, amid tight security and an atmosphere of togetherness amid adversity. Families of the victims, holding each other for support, marched in the front along with the leaders, along with journalists working for newspaper Charlie Hebdo, the target of the attack that started three days of terror. Several wept openly.
"I Am Charlie," read legions of posters and banners. Many waved editorial cartoons, and the French tricolor and other national flags.
The leaders marched down Voltaire Boulevard -- named after the Enlightenment-era figure who symbolizes France's attachment to freedom of expression. One marcher bore a banner with his famed pledge: "I do not agree with what you say, but I will fight to the death to defend your right to say it."
"It's important to be here for freedom for tolerance and for all the victims. It's sad we had to get this point for people to react against intolerance racism and fascism," said Caroline Van Ruymbeke, 32.
The three days of terror began Wednesday when brothers Said and Cherif Kouachi stormed the newsroom of Charlie Hebdo, killing 12 people. Al Qaeda's branch in Yemen said it directed the attack by the masked gunmen to avenge the honor of the Prophet Muhammad, a frequent target of the weekly's satire. Charlie Hebdo assailed Christianity, Judaism as well as officialdom of all stripes with its brand of sometimes crude satire that sought to put a thumb in the eye of authority and convention.
On Thursday, police said Coulibaly killed a policewoman on the outskirts of Paris and on Friday, the attackers converged. While the Kouachi brothers holed up in a printing plant near Charles de Gaulle airport, Coulibaly seized hostages inside a kosher market. It all ended at dusk Friday with near-simultaneous raids at the printing plant and the market that left all three gunmen dead. Four hostages at the market were also killed.
Five people who were held in connection with the attacks were freed late Saturday, leaving no one in custody, according to the Paris prosecutor's office. Coulibaly's widow is still being sought and was last traced near the Turkey-Syrian border.
Early Sunday, police in Germany detained two men suspected of an arson attack against a newspaper that republished cartoons from Charlie Hebdo. No one was injured in that attack.
"The terrorists want two things: they want to scare us and they want to divide us. We must do the opposite. We must stand up and we must stay united," French Foreign Minister Laurent Fabius told French TV channel iTele on Sunday.
France remains on high alert while investigators determine whether the attackers were part of a larger extremist network. More than 5,500 police and soldiers were being deployed on Sunday across France, about half of them to protect the march. The others were guarding synagogues, mosques, schools and other sites around France.
"I hope that we will again be able to say we are happy to be Jews in France," said Haim Korsia, the chief rabbi in France, who planned to attend the rally.
At an international conference in India, U.S. Secretary of State John Kerry said the world stood with the people of France "not just in anger and in outrage, but in solidarity and commitment to the cause of confronting extremism and in the cause that extremists fear so much and that has always united our countries: freedom."
Posthumous video emerged Sunday of Coulibaly, who prosecutors said was newly linked by ballistics tests to a third shooting -- the Wednesday attack on a jogger in a Paris suburb that left the 32-year-old man gravely injured. In the video, Coulibaly speaks fluent French and broken Arabic, pledging allegiance to the Islamic State group and detailing the terror operation he said was about to unfold.
The Kouachi brothers claimed the attacks were planned and financed by al Qaeda in Yemen.
In the United States, it was standing room only during a vigil at Lincoln Square Synagogue on Manhattan's Upper West Side, CBS2's Hazel Sanchez reported.
Local leaders and prominent figures, including French Consul General Bertrand Lotholary and Chelsea Clinton, lit candles in memory of the victims in Paris.
"We in New York know the horror of terrorism unfortunately more than most places," said Sen. Charles Schumer. "And we want to say to our French breatheren, we stand with you."
On Saturday, hundreds also gathered at Washington Square Park to honor the victims.
"We have to show our solidarity with the people who had the courage to stand up to Islamist fascism," said Curtis Ellis.
Sally lives in Paris and is visiting New York.
"I arrived last night. So I'm going to be here to support all my French friends that live here and support everybody in France right now, everybody that's suffering," she said.
Many at the vigil held up pens in silent tribute to the cartoonists who were killed in the shooting rampage at the Charlie Hebdo satirical newspaper in Paris on Wednesday.
"We are from France and so we knew what happened and we are really sad for that," 7-year-old Antoine Hotellier told CBS2's Matt Kozar.
The Empire State Building was lit up in honor of the victims in the Paris terror attacks on Sunday night. The tower shone its lower lights in blue, white and red -- the colors of the French national flag. The lights were dimmed for 5 minutes of remembrance at 8 p.m.
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