Hacking group Anonymous has declared war on ISIS in a new YouTube video following the horrific attacks in Paris on Friday night which left 129 people dead.

In a newly released video on the group's French YouTube page, the Anonymous hackers warn the terror group to 'expect us' because its members 'are going to hunt you down'.

The hacktivitst group joined those condemning the terror attacks in Paris on Friday night and vowed to hunt down those responsible online and expose them.

In a newly released video on the group's French YouTube page, the anonymous hackers (pictured) warn the terror group to 'expect us' because its members from all over the world are going to 'hunt you down'

In the video, and wearing the group's signature Guy Fawkes mask, a spokesman says in French: 'Anonymous from all over the world will hunt you down. You should know that we will find you and we will not let you go.'

He continues: 'We will launch the biggest operation ever against you.

'Expect massive cyber attacks. War is declared. Get prepared.

'The French people are stronger than you and will come out of this atrocity even stronger.'

The hacktivists already publish and update a list of Twitter accounts they claim spread propaganda in support of ISIS.

Now for Operation Paris, or #OpParis, the group is urging its members to hack into ISIS wesites to steal valuable information and leak it online.

The group's official Twitter page claims to have already hacked and taken down 2256 pro-ISIS Twitter accounts.

The group used harrowing images from Friday's attack like this one (pictured) in the video for #OpParis

The hacktivists publish and update a list of Twitter accounts they claim spread propaganda in support of ISIS

The group launched a similar attack on the terror group following the Charlie Hebdo massacre in January and closed down an extremist website.

ISIS has claimed responsibility for the Paris atrocities which killed at least 129 people on Friday night.

French forces struck back with a massive bombardment of the jihadist group's stronghold in Raqqa, Syria, last night.

Twelve aircraft, including 10 fighter jets, dropped 20 bombs, destroying a jihadi training camp and a munitions dump in Raqqa, where Iraqi intelligence officials claimed the attacks on Paris were planned.

British police and spies are working closely with counterparts in France and Belgium to identify and pursue those behind the Paris massacre.

Security has been beefed up in UK cities and ports as Britons were urged to remain vigilant, although the terror threat level has not been changed from the second-highest 'severe' rating.

During the series of coordinated attacks in Paris gunmen burst into a concert hall shouting 'Allahu Akbar'. Pictured: A victim under a blanket outside the concert hall following the massacre

A bloodied survivor of one of the Paris attacks talks on the phone as he is escorted from the scene by police

A woman is evacuated from the scene of the massacre, where witnesses said gunmen threatened to kill anyone who moved

Victims lay on the pavement outside La Bell Equipe restaurant on Friday evening following the attacks