British officials blamed Russia on Thursday for a cyber-attack in 2017 which disrupted companies across Europe including UK-based Reckitt Benckiser.
Russia has previously denied the accusations of being behind the attack and pointed out that Russian firms were among those whose systems were affected.
Known as NotPetya, the attack took place in June and the virus was first spread across Ukraine where it crippled government and business computers before extending around the world.
Britain’s foreign ministry said the attack originated from the Russian military, according to Reuters.
“The decision to publicly attribute this incident underlines the fact that the UK and its allies will not tolerate malicious cyber activity,” the ministry said in a statement, adding that: “the attack masqueraded as a criminal enterprise but its purpose was principally to disrupt.”
“Primary targets were Ukrainian financial, energy and government sectors. Its indiscriminate design caused it to spread further,” the statement said.
British defence minister Gavin Williamson said the attack was part of a new era of warfare and Britain had to be ready to respond.
“We must be primed and ready to tackle these stark and intensifying threats,” he said in a statement.
Moscow has denied the accusations again on Thursday. Kremlin spokesman Dmitry Peskov said Russia “categorically denies the allegations.”
“We consider (them)… groundless,” he added.
Last November, Prime Minister Theresa May accused Russia of meddling in elections and planting fake stories in the media.