The White House said June's NotPetya ransomware attack caused billions of dollars in damage across Europe, Asia, and the Americas.

UK Defence Secretary Gavin Williamson said Russia was "ripping up the rule book" and the UK would respond.

Moscow denies being behind the attack, calling such claims "Russophobic".

Experts believe about 2,000 NotPetya attacks were launched, mainly aimed at Ukraine. The country Ukraine has been locked in a simmering conflict with Russian-backed separatists since Moscow annexed Crimea in 2014.

On Thursday the UK government took the unusual step of publicly accusing the Russia military of being behind the attack.

"The UK and its allies will not tolerate malicious cyber activity," the foreign office said in a statement. Later, the White House also pointed the finger at Russia.

"In June 2017, the Russian military launched the most destructive and costly cyber-attack in history," a statement said.

"This was also a reckless and indiscriminate cyber-attack that will be met with international consequences."

Russia, however, said the claims were "groundless" and that Russian businesses were among those whose systems were affected.

"It's not more than a continuation of the Russophobic campaign," Kremlin spokesman Dmitry Peskov said.