Paris: More than 150,000 people turned up to hold vigils in silence in Paris and other cities of France on Wednesday night, even as mourners across France observed a minute of silence today to honour the 12 terror victims.
The world famous Eiffel Tower will go black at 8 pm Thursday night in memory of the victims.
Outside the historic Notre-Dame Cathedral in Paris some mourners wept as the church bells rang out to commemorate the dead.
French Prime Minister Francois Hollande, who had called for the silence, observed it with police at the Prefecture of Police of Paris.
Afterwards he shook hands with police standing in line outside the building.
At the Place de la Republique in the city centre, where crowds had gathered on Wednesday evening for a vigil, crowds observed the silence followed by a sustained applause.
More than 150-thousand people gathered for vigils across France on Wednesday night to pay tribute to victims of an attack on the satirical paper 'Charlie Hebdo' earlier in the day.
Demonstrators gathered in silence in central squares in various French cities holding up placards with the phrase, "Je suis Charlie" (I am Charlie) and pens to honour the victims.
Masked gunmen stormed the offices of the newspaper, methodically killing 12 people, including the editor, before escaping in a car on Wednesday morning.
The French flag was flown at half mast across Europe on Thursday.
France raised its terror alert system to the maximum and bolstered security with more than 800 extra soldiers to guard media offices, places of worship, transport and other sensitive areas.
A minute of silence was observed across Europe, by the European Parliament in Brussels, police officers at London's Scotland Yard as well as a crowd in Trafalgar Square.
French President Francois Hollande ordered flags to be flown at half mast on Thursday, which was observed by French embassies in capitals across Europe, including Rome and Moscow, where locals left flowers and messages of condolence.
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 weren't from the media world, expressing solidarity and support of freedom of speech.
Similar gatherings, including some silent vigils, took place at London's Trafalgar Square, in front of the Brandenburg Gate in Berlin, in Madrid, Brussels, Nice 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 London student who is originally from Paris and was among those in the London crowd, estimated in the hundreds.
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 Muhammad.
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."
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. (hash)IamCharlie."
Masked gunmen methodically killed the 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.
Blanc, in London, held up a quote often attributed to Voltaire: "I do not agree with what you have to say, but I will defend to death your right to say it."
About 1,000 people gathered near the European Union's headquarters in Brussels to express sympathy and outrage. In Spain, about 200 people in Madrid gathered outside the French Embassy to voice outrage. Some also held pens in the air and chanted "Freedom of Expression" and "We Are All Charlie."
French students in Stockholm organized about 100 people to lay flowers and candles in front of the French Embassy in Stockholm.
A handful of women in the swank Roman piazza where the French Embassy is located had "Je suis Charlie" banners taped to their jackets.
"I still cannot believe what happened," said protester Linda Chille. "It is cruel and very shocking."