Hundreds of thousands of people joined by dozens of world leaders are attending a rally through Paris to honour the 17 people killed in some of the worst attacks on French soil, Al Jazeera reported.
Among those attending Sunday's march are family members of the 12 people killed during the massacre at the Charlie Hebdo weekly, a satirical publication that often published cartoons lampooning revered religious figures.
Assailants also targeted a kosher supermarket and police, killing five people.
Each of the families of the Charlie Hebdo staff wore a white bandana on their head with the word "Charlie" written across.
About 2,200 security personnel will guard the route of the march, which will run 3km from the historic Place de la Republique to Place de la Nation in the east of Paris, France's interior minister said, with snipers stationed on rooftops.
French media estimated up to 3 million were taking part, with the interior ministry saying the rally was "unprecedented".
The numbers in Sunday's rally were more than those of the marchers who took to Paris streets when the Allies liberated the city from the Nazis in World War II, the ministry said.
Some of the foreign dignitaries attending the event include David Cameron, British prime minister; Mariano Rajoy, Spain's prime minister; German Chancellor Angela Merkel along with Sigmar Gabriel, vice-chancellor and energy minister, and Frank-Walter Steinmeier, the foreign minister.
Others dignitaries are Benjamin Netanyahu, Israel's prime minister, and Mahmoud Abbas, Palestinian president, as well as Ukraine's President Petro Poroshenko.
Jordan's King Abdullah II and Queen Rania are also attending the march.