Gunmen have attacked the Paris office of French satirical magazine Charlie Hebdo, killing 11 people and injuring 10, French officials say.

Witnesses spoke of sustained gunfire at the office as the attackers opened fire with assault rifles before escaping.

Police have launched a major operation in the Paris area in their hunt for the attackers.

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.