The online hacker group Anonymous has promised to take aim at ISIS in a video posted online following Friday’s devastating attacks on Paris.

“These attacks cannot go unpunished, hence the reason why the Anonymous from all over the world will hunt you down as we did since the attacks of Charlie Hebdo,” a masked speaker in the video says in French. “Therefore, be prepared for a massive retaliation from Anonymous.”

The speaker goes on to say that Anonymous is ‘declaring war’ on ISIS and will launch “massive” cyber-attacks against the group.

The video comes as the Western world begins to formulate its own response to the coordinated shooting and bombing attacks in Paris that left 129 people dead and hundreds of others injured Nov. 13.

On Monday French President Francois Hollande said he would like to see the United States and Russia work together to ramp up their efforts against the extremist group, which has vowed to continue attacking targets in France and the West.

Speaking at the G20 summit in Turkey Monday, U.S. President Barack Obama said the U.S. will step up its actions against ISIS, but will stick to its current strategy of airstrikes and arming moderate forces.

- With files from the Associated Press.