France president, Francois Hollande has declared Thursday 8 January as a day of national mourning for the victims of a terrorist attack on a Parisian satirical weekly, Charlie Hebdo.

He made the declaration in a sombre TV address Wednesday. The symbolic day will be only the fifth in the past 50 years — after the worst attack on French soil in decades.

The Paris attack on Charlie Hebdo, a magazine that has long been in confrontation with Islamists, triggered impromptu demonstrations of solidarity in cities across the world, including Moscow, Washington, London and Tokyo.

More than 100,000 gathered across France, many protesters carrying banners reading: “I am Charlie” while the hashtag #JeSuisCharlie was trending worldwide including in Arabic.

Hollande called the massacre “an act of exceptional barbarity” and “undoubtedly a terrorist attack.”

“Nothing can divide us, nothing should separate us. Freedom will always be stronger than barbarity,” said the president, who ordered flags flown at half-mast for the next three days.

As Hollande addressed compatriots, French anti-terror police launched a late-night raid in a northeastern city Wednesday in a frantic manhunt for the masked gunmen who shouted “Allahu akbar” as they killed 12 people at a satirical weekly in Paris, sparking global outrage.

Local television showed black-clad sharpshooters from the elite police unit in the streets of Reims, in France’s Champagne region, as unconfirmed media reports named three suspects in the attack, including two brothers.

Several thousand police were deployed to find the gunmen and parts of the French capital were in lockdown as the killers remained on the loose.

Charlie Hebdo gained notoriety in February 2006 when it reprinted cartoons of the Prophet Mohammed that had originally appeared in Danish daily Jyllands-Posten, causing fury across the Muslim world.

The killers on Wednesday screamed “we have avenged the prophet, we have killed Charlie Hebdo”, according to prosecutors.

– ‘Could they come here?’ –

The drama began in broad daylight in a quiet Paris street when the gunmen stormed into the weekly’s offices as the journalists were in an editorial meeting, first shooting a person in the reception area.

They picked off eight journalists, including some of France’s best-known cartoonists, a security guard and a visitor. One person survived by hiding under a table.

Chilling amateur video footage filmed after the carnage then showed them outside, running toward a wounded policeman as he lay on the pavement.

One attacker says: “You wanted to kill me?” before coldly shooting the officer dead.

Large numbers of police and ambulances rushed to the scene and reporters saw bullet-riddled windows and people being carried out on stretchers.

Prosecutors said 11 people were also injured in the attack, with four in critical condition.

One man who witnessed the attack described a scene like “in a movie”.

“I saw them leaving and shooting. They were wearing masks. These guys were serious,” said the man who declined to give his name. “At first I thought it was special forces chasing drug traffickers or something.”

Authorities said the gunmen’s professional and calculating manner suggested they had been well-trained.