Many who poured into Place de la Republique in eastern Paris near the site of Wednesday's noontime attack waved papers, pencils and pens. Journalists led the march but most in the crowd were not from the media world, expressing solidarity and support of freedom of speech.
Similar gatherings took place at London's Trafalgar Square, in front of the Brandenburg Gate in Berlin, in Madrid, Brussels, Nice and elsewhere.
Online, the declaration "Je Suis Charlie," or "I Am Charlie," replaced profile pictures on Facebook while Twitter users showed themselves with the slogan on signs with words of support for the 12 victims who were killed at Charlie Hebdo, a weekly newspaper that had caricatured the Prophet Mohammad.
The "Je Suis Charlie" slogan grew into a trending hashtag on Twitter and spread to Instagram, along with an image of a machine gun with the words "Ceci n'est pas une religion," or "This is not a religion."
Masked gunmen methodically killed 12 people, including the newspaper's editor, as they shouted "Allahu Akbar!" - or "Allah is the greatest" - while firing, then fleeing in a car.
The newspaper's depictions of Islam have drawn condemnation and threats before. It was firebombed in 2011 and also satirized other religions and political figures.
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