Black-hooded gunmen shot dead and 11 others killed at the Paris office of the Satirical newspaper Charlie Hebdo, a publication firebombed in the past after publishing cartoons lampooning Muslim leaders and the Prophet Mohammad, police said.
Witnesses spoke of sustained gunfire at the office as the attackers opened fire with assault rifles before escaping.
President Francois Hollande headed to the scene of the attack and the government said it was raising France’s security level to the highest notch.
“This is a terrorist attack, there is no doubt about it,” Hollande told reporters.
Another 10 people were injured in the incident and police union official Rocco Contento described the scene inside the offices as “carnage”.
“About a half an hour ago two black-hooded men entered the building with Kalashnikovs (rifles),” witness Benoit Bringer told the TV station.
“A few minutes later we heard lots of shots,” he said, adding that the men were then seen fleeing the building.
Charlie’s latest tweet was a cartoon of the Islamic State militant group leader, Abu Bakr al-Baghdadi.
The Satirical weekly has courted controversy in the past with its irreverent take on news and current affairs.
The magazine was fire-bombed in November 2011 a day after it carried a caricature of the Prophet Muhammad.
UK Prime Minister David Cameron said in a tweet: “The murders in Paris are sickening. We stand with the French people in the fight against terror and defending the freedom of the press.”