Police officers secure access to a residential building during investigations in the eastern French city of Reims January 8, 2015, after the shooting against the Paris offices of Charlie Hebdo, a satirical newspaper.[Photo/Agencies]

The masked, black-clad men with assault rifles stormed the offices near Paris' Bastille monument in the Wednesday noontime attack on the publication, which had long drawn condemnation and threats _ it was firebombed in 2011 - for its depictions of Islam, although it also satirized other religions and political figures.

Shouting "Allahu akbar!" as they fired, the men used fluent, unaccented French as they called out the names of specific employees.

Artist Corinne Rey told the French newspaper L'Humanite that she punched in the security code to the Charlie Hebdo offices after she and her young daughter were "brutally threatened" by the gunmen.

Eight journalists, two police officers, a maintenance worker and a visitor were killed, said prosecutor Francois Molins. He said 11 people were wounded - four of them seriously.

After fleeing, the attackers collided with another vehicle, then carjacked another car before disappearing in broad daylight, Molins said.

Among the dead: the paper's editor, Stephane Charbonnier.

The staff was in an editorial meeting and the gunmen headed straight for Charbonnier - widely known by his pen name Charb - killing him and his police bodyguard first, said Christophe Crepin, a police union spokesman.

Rey said the assault "lasted five minutes. I hid under a desk."

Two gunmen strolled out to a black car waiting below, one of them calmly shooting a wounded police officer in the head as he writhed on the ground, according to video and a man who watched in fear from his home across the street.

The witness, who refused to allow his name to be used because he feared for his safety, said the attackers were so methodical he first thought they were members of France's elite anti-terrorism forces. Then they fired on the officer.

"They knew exactly what they had to do and exactly where to shoot. While one kept watch and checked that the traffic was good for them, the other one delivered the final coup de grace," he said.

"Hey! We avenged the Prophet Muhammad! We killed Charlie Hebdo," one of the men shouted in French, according to video shot from a nearby building.