K intelligence chiefs claimed the GRU were behind four brand new strikes, in what they described as a “flagrant violation of international law”.
The National Cyber Security Centre (NCSC) has identified the GRU as responsible for the provocative attacks.
It comes as Dutch Defence Minister Ank Bijleveld said the Netherlands disrupted an attempt in April by Russian intelligence agents to hack the Organization for the Prohibition of Chemical Weapons.
Four Russians were expelled following the alleged cyber attack.
And Britain is now poised to strike back against Russia, with Foreign Secretary Jeremy Hunt pledging to retaliate hard.
Mr Hunt said: “These cyber attacks serve no legitimate national security interest, instead impacting the ability of people around the world to go about their daily lives free from interference, and even their ability to enjoy sport.
“The GRU’s actions are reckless and indiscriminate: they try to undermine and interfere in elections in other countries; they are even prepared to damage Russian companies and Russian citizens.
“This pattern of behaviour demonstrates their desire to operate without regard to international law or established norms and to do so with a feeling of impunity and without consequences.
“Our message is clear: together with our allies, we will expose and respond to the GRU’s attempts to undermine international stability.”
But Russia has hit back at what is has called a “diabolical perfume cocktail” of allegations by someone with a “rich imagination”.
Defence Secretary Gavin Williamson, attending a Nato summit in Brussels, said the UK and its allies were united against Russia.
Mr Williamson said to Sky News: “And what we are seeing is that Russia is quite willing to use such weapons such as cyber attacks against these organisations, and here at Nato we stand shoulder to shoulder with our allies in unity against such actions.
“What we have made clear is that we are not going to be backward leaning. We are going to actually make it clear where Russia acts that we are going to be exposing that action.
“And we believe that by doing so this will act as a disincentive for acting in such a way in the future.”
US Defence Secretary Jim Mattis today spoke in support of the UK and Netherlands.
Mr Mattis said: “We are ready today to provide cyber support to our allies, I’ve seen enough of the evidence to say that the Dutch and the British are 100 percent accurate in who they have attributed this to.”
The tough response is likely to add further pressure to the strained relationship between the UK and Russia following the Salisbury nerve agent attack in March.
Prime Minister Theresa May has said GRU officers were behind the Novichok poisoning on ex-Russian spy Sergei Skripal.
Mr Skripal and his daughter Yulia Skripal were left fighting for their lives following the incident.
And Dawn Sturgess, who later came into contact with the same nerve agent with her partner Charlie Rowley, died in July following the exposure to the deadly poison.
But Mr Putin has repeatedly denied any involvement in the attack.
Speaking yesterday, the Russian President said: “We didn’t need to poison anyone over there.
“This traitor Skripal was caught, he was punished and did five years in prison.
“We let him go, he left the country and he continued to cooperate there and consult some intelligence services. So what?”