12 dead at the hands of gunmen.
Charlie Hebdo editor Stephane Charbonnier, 47, had received death threats in the past and was living under police protection.
French media have named the three other cartoonists killed in the attack as Cabu, Tignous and Wolinski. The attack took place during the magazine's daily editorial meeting.
At least seven people were wounded in the attack, with several in critical condition.
The satirical weekly has courted controversy in the past with its irreverent take on news and current affairs. It was fire-bombed in November 2011 a day after it carried a caricature of the Prophet Muhammad.