French hackers from the activist group Anonymous have declared "war" on Islamic State after the Paris attacks.

In a video posted on YouTube, a representative wearing a hood and the group's distinctive Guy Fawkes mask said the violence that left 129 people dead "can't go unpunished".

The statement said: "That's why Anonymous activists from all over the world will hunt you down. Yes, you, the vermin who kill innocent victims, we will hunt you down like we did to those who carried out the attacks on Charlie Hebdo.

"So get ready for a massive reaction from Anonymous. Know that we will find you and we will never let up.

"We are going to launch the biggest ever operation against you - expect very many cyber-attacks.

"War is declared. Prepare yourselves. Know this, the French people are stronger than you and will come out of this atrocity even stronger."

The declaration is not the first time the "hacktivist" group has targeted Islamic State.

After the Charlie Hebdo attacks in January, a Belgian offshoot of the group said it was "declaring war" against "al Qaeda, Islamic State and other terrorists".

It later boasted about shutting down a French website associated with extremists and helping get 1,500 IS-supporting Twitter and Facebook accounts off line.

Anonymous first emerged in 2003 and has become known for a series of well-executed public attacks on corporations, religious and governmental bodies.

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