The British government says that Russia was behind a massive global cyberattack that hit major companies in June 2017.
Foreign Office minister Tariq Ahmad said in a statement on Thursday that the Russian military was responsible for the attack, which initially targeted computers in Ukraine but quickly spread beyond its borders.
The attack -- called NotPetya -- hit companies including British advertising group WPP, Oreo maker Mondelez, U.S. drugmaker Merck and global shipping company FedEx.
"The destructive attack masqueraded as ransomware, but its purpose was principally to disrupt," the U.K. government said in a statement.
"The decision to publicly attribute this incident reiterates the position of the U.K. and its allies that malicious cyber activity will not be tolerated," it added.
The Russian government said it "categorically denied the accusations."
"We think they have no basis and no foundation, and this is nothing else but the continuation of the Russophobic campaign," Dmitry Peskov, a spokesman for President Vladimir Putin, told reporters.
Ahmad said the attack had disrupted organizations across Europe, costing them hundreds of millions of pounds.
In September, FedEx attributed a $300 million loss to the attack. The company's subsidiary, TNT Express, was forced to suspend business.