Anonymous, the online "hacktivist" collective, has announced that it will avenge the attack on Charlie Hebdo by rendering jihadist websites inaccessible.

The group published a video on YouTube through its Anonymous Belgique channel, as well as a statement posted on Pastebin.

The statement, in French, calls on all computer users to join them in their campaign against jihadist sites through a distributed denial of service (DDoS) attack.

"Freedom of expression has suffered an inhuman assault," the statement reads. "Sickened, shocked, we cannot fall to the ground. It is our duty to react.

"It is clear that some people do not want, in a free world, this inviolable and sacred right to freely express opinions. Anonymous will never let this right be violated by obscurantism and mysticism. We will always fight the enemies of freedom of expression everywhere."

Recent Anonymous campaigns have offered support to pro-democracy protesters in Hong Kong by attacking Chinese government websites, as well as attempting to take down government and company websites following the sabotage of online file-sharing site The Pirate Bay.

The attack on Charlie Hebdo, the satirical French magazine, left 12 people dead and 11 injured on Wednesday.

The two suspects have been linked by intelligence officials to militant groups and were heard shouting Islamist slogans as they carried out the massacre.

A huge police operation is currently ongoing in an effort to capture the perpetrators, currently surrounded by police in a building in north-east Paris.

"Freedom of expression and opinion is a non-negotiable thing to tackle - to attack it is to attack democracy," Anonymous' statement concludes.

"Expect a massive and head-on reaction on our part because the defence of those freedoms is the foundation of our movement."