The interior ministry said nearly four million people took to the streets across the country on Sunday, with some estimates putting the number in Paris alone at 1.6 million.

At the head of a vast and colourful procession in the capital, President Francois Hollande linked arms with world leaders, including the Israeli Prime Minister and the Palestinian President, in an historic display of unity.

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A sea of humanity flowed through the streets to mourn the victims of three days of terror that began with a slaughter at the offices of satirical magazine Charlie Hebdo on Wednesday and ended with 17 dead.

The crowd brandished banners saying "I'm French and I'm not scared" and, in tribute to the murdered cartoonists, "Make fun, not war" and "Ink should flow, not blood."

Emotions ran high in the grieving City of Light, with many people in tears as they came together under the banner of freedom of speech after France's worst terrorist bloodbath in half a century.

Isabelle Dahmani, a French Christian married to a Muslim, Mohamed, brought the couple's three young children to show them there is nothing to fear.

Their nine-year-old daughter had burst into tears as she watched TV pictures of heavily armed Islamist brothers Said and Cherif Kouachi attacking the magazine's offices, Isabelle said, recalling she had asked if "the bad men are coming to our house?"

The victims' mourning families played a prominent role in the march, alongside representatives from around 50 countries.

In an emotional scene, Charlie Hebdo columnist Patrick Pelloux fell sobbing into the arms of Hollande.

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With so many world leaders present, security in the still jittery capital was tight, with police snipers stationed on rooftops and plain-clothes officers among the crowd.

"Today, Paris is the capital of the world," Hollande said. "The entire country will rise up."

Hundreds of thousands of people turned out in other French cities including Bordeaux and Lyon and marches were held in Berlin, Brussels, Istanbul and Madrid and in US and Canadian cities as well.

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Ban welcomes Paris march against terrorism

UN Secretary General Ban Ki-moon welcomed the march in Paris, held in memory of the victims of last week's terrorist attacks in France and to protest against terrorism anywhere in the world.

Ban, in a statement issued by his spokesperson, renewed his condolences to the families of the victims of the attacks on the Charlie Hebdo magazine and a kosher supermarket, and of the policewoman who was murdered in Paris, according to a report.

A massive march was held Sunday in the French capital, in which about 1.5 million people were known to have participated, apart from world leaders, including German Chancellor Angela Merkel, British Prime Minister David Cameron, Israeli Prime Minister Benjamin Netanyahu, Palestinian leader Mahmoud Abbas, French President Francois Hollande and others.

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Staffan de Mistura, the UN secretary general's special envoy, represented the UN at the march.

Ban was deeply moved by the images from the march and the displays of global solidarity over the past few days."He is strongly committed to the essential work of countering extremism, fighting anti-Semitism and other forms of discrimination, and upholding the rights to freedom of speech and expression," the statement said.

The UN secretary general called for "heightened efforts" to promote tolerance and understanding. "The world must address this violence and division in ways that do not exacerbate the problems and that ensure respect for human rights and the rule of law," Ban said.

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