Messages of condolence, outrage and defiance over the Paris terrorist attack on a newspaper office spread around the world Wednesday with thousands of people taking to the streets to protest the killings and using the slogan "Je Suis Charlie" -- I am Charlie -- on social media.
Many of the thousands of people who poured into Place de la Republique in eastern Paris near the Charlie Hebdo offices waved papers, pencils and pens. Journalists led the march, but most in the crowd were from other walks of life, 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, Rome, Stockholm and elsewhere.
"No matter what a journalist or magazine has to say, even if it is not what the majority of people think, they still have the right to say it without feeling in danger, which is the case today," said Alice Blanc, a student originally from Paris who was in the London crowd.
Online, the declaration "Je Suis Charlie" replaced profile pictures on Facebook. "#JeSuisCharlie" 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."
One user on Instagram sent out a simple black-and-white drawing of the Eiffel Tower with the message: "Pray for Paris." Another wrote: "Islam is a beautiful religion. This is not what we see on TV. Terrorists are not real Muslims."
In other corners of Twitter, self-proclaimed jihadis celebrated with hashtags such as #ParisInvasion. "Mock the Prophet of Islam and pay with your life," reads a rough translation of one tweet.
Anti-immigrant, right-wing parties in the Europe seized on the attacks.
"Time's up for denial and hypocrisy," said Marine Le Pen, who leads France's National Front.
"Any incident like the one in Paris will only be fuel to the fire," Joerg Forbrig, the senior program director at the German Marshall Fund of the United States, which promotes transatlantic cooperation, said by phone from Berlin. "It will be welcomed as a 'told-you-so' episode by radical movements saying Islam is a threat to our countries."