Several public NATO websites suffered downtime after being successfully targeted in a cyber-attack which has been traced back to the Ukraine.

A group who go by the name ‘Cyber Berkut’ stated that they were behind the attack as they aren’t happy with NATO’s interference in Ukrainian affairs.

A statement released on their website read, “We, Cyber Berkut, announce that today at 6:00 p.m. we started the cyberattack on NATO resources. We, Cyber Berkut, will not allow the presence NATO occupation on the territory of our homeland, because it opposes NATO intervention in Ukraine.”

The main NATO website was affected along with a cyber-security centre in Estonia which is linked to the alliance. NATO has yet to confirm the source of the attack but have claimed that none of their essential systems had been compromised.

A spokeswoman for the alliance Oana Lungescu stated, “Our experts working to restore normal function. No operational impact … The attack hasn’t affected the integrity of Nato’s systems.”

John Bumgarner who is the chief technology officer at the US Cyber Consequences Unit claims that all of the evidence that has been collected so far, points in the direction of pro-Russian sympathisers being behind the attacks.

Bumgarner stated, “One could equate these cyber attacks against Nato as kicking sand into one’s face.”

Tensions between Russia and the West have intensified ever since Russian forces entered Ukrainian territory in the Crimea region after former Prime Minister Viktor Yanukovych was overthrown.

Ukrainian and Russian websites have both been targets for cyber-attacks in recent weeks but this appears to be the first major attack on a Western website since the crisis began.