Paris mayor Anne Hidalgo has expressed her "feeling of absolute horror" at the terrorist attack against the satirical weekly Charlie Hebdo on Wednesday, which killed at least 12 including two police officers and top staff members of the newspaper.

In a statement published online by French media like Le Figaro, the mayor conveyed her sympathies to the "martyred victims of Liberty, the freedom of the press, pillar of democracy and the French Republic".

"This massacre has left our country, our city and our democracy bereaved," Ms Hidalgo wrote.

"We have just been hit in the heart of our liberty.

"We have to react to this act according to the principles of the Republic."