Security at places of worship in Paris has been reinforced following today's shooting at satirical newspaper Charlie Hebdo, in which 12 people have been confirmed dead.

France has upped security at places of worship, shops media offices and transportation.

There was prolonged gunfire as the attackers opened fire with assualt rifles at the Charlie Hebdo offices, before driving off. The car was later found abandoned in northern Paris.

Police have confirmed 12 people have died, including the magazine's editor, three other cartoonists and two police officers.

France's President, Francois Hollande, has visited the scene. He said it was without doubt a terrorist attack.

"Nobody in France should think that they can behave against the principle of the Republic and harm the spirit of the Republic, embodied by a newspaper," President Hollande said. "Today I am thinking about the victims... We should do whatever we can to find those responsible and to call for national unity."

David Cameron condemned the attack as "sickening" and said Britain stood with France in the fight against terror.

"The murders in Paris are sickening. We stand with the French people in the fight against terror and defending the freedom of the press," Cameron said in a statement on his official Twitter feed.

A firebomb attack gutted the headquarters of Charlie Hebdo in November 2011 after it put an image of the Prophet Mohammad on its cover.

Additional reporting by Reuters