PARIS, Jan. 7  -- The office of Paris Prosecutor of the Republic confirmed at least 12 people were killed on Wednesday in a shooting at the Paris office of Charlie Hebdo, a satirical newspaper, adding four others were seriously wounded in the "terror attack."

France has raised anti-terrorism alert in the greater Paris area to the highest level after the shooting amid fears of eventual attacks in the region, because the perpetrators have fled away, raising risks of eventual shooting in the French capital.

"Without doubt, it's a terrorist attack against an office that has been threatened several times, which is why it was protected," French president Francois Hollande said visiting the shooting scene.

"They will be hunted down and brought to justice," the president stressed.

France, the target of Islamist fighters in reprisal for its military strikes against Islamist strongholds in Iraq and the Sahel region, has aborted several terror attacks in recent weeks, Hollande said.

An emergency government meeting was due in the Elysee to evaluate the situation and take the adequate measures to avoid further attacks.

In November 2011, the headquarters of Charlie Hebdo was fire bombed after it put an image of the Prophet Mohammed on its cover.