French President Francois Hollande (C) arrives after a shooting at the Paris offices of Charlie Hebdo, a satirical newspaper, January 7, 2015.

French President Francois Hollande described “unity” as his country’s “best weapon” after suspected extremist militants killed 12 people in an against a satirical paper in Paris on Wednesday.

“Nothing can divide us, nothing should separate us. Freedom will always be stronger than barbarity,” Hollande said in a televised address to the nation after the attack, which is considered to be France’s deadliest such attack in more than half a century.

Thursday will also mark the fifth time in the last 50 years France has declared a day of mourning.

He praised the “courageous chroniclers” of the satirical Charlie Hebdo magazine. Four of the 12 who were killed were Charlie Hebdo staff, including the editor-in-chief Stephane Charbonnier and famous cartoonist Jean Cabut.

It is not the first time the paper has faced a violent encounter with Islamists. In 2011, Charlie Hebdo’s offices were destroyed in a firebombing after it announced a special “Charia Hebdo” edition with Islam’s Prophet Mohammed jokingly referred to as guest editor.

The last tweet published by Charlie Hebdo featured a picture mocking ISIS leader Abu Bakr al-Baghdadi wishing him good health.

“Through their influence, their insolence and their independence, they touched the French generation after generation,” Hollande said.

He added: “We will continue to defend this message of freedom in their name.”

When visiting the scene of the attack, Hollande called the assault “an act of exceptional barbarism.”

[wpResize]