The United States on Thursday publicly blamed Russia for carrying out the so-called NotPetya cyber-attack last year that crippled government and business computers in Ukraine before spreading around the world.

The statement by the White House came hours after the British government attributed the attack to Russia, a conclusion already reached and made public by many private sector cyber security experts.

The attack in June of 2017 'spread worldwide, causing billions of dollars in damage across Europe, Asia and the Americas,' White House Press Secretary Sarah Sanders said in a statement.

'It was part of the Kremlin´s ongoing effort to destabilize Ukraine and demonstrates ever more clearly Russia´s involvement in the ongoing conflict,' Sanders added.

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

The Kremlin denies Russia was responsible for the 'NotPetya' cyber-attack last year

Britain's foreign minister for cyber security earlier said the Kremlin was responsible for 'malicious cyber activity'.

The attack last year targeted Ukraine and spread across Europe. Its primary targets were the Ukrainian financial, energy, and government sectors.

Ukraine has been locked in a simmering conflict with Russian-backed separatists since Moscow annexed Crimea in 2014.

But it was designed to spread further and affected other European and Russian firms in June.

Kremlin spokesman Dmitry Peskov said on Friday he denies Russia was responsible for the 'NotPetya' cyber-attack last year, after the White House on Thursday joined the British government in accusing Moscow of the attack.

In response to a question about the attack, he said he reiterated comments made on Thursday, when he said that the allegations by a British official about 'NotPetya' attack were groundless and part of a 'Russophobic' campaign being conducted in some Western countries.

Britain's Defence Secretary Gavin Williamson accused Vladimir Putin of 'ripping up the rule book'.

He told the Daily Mail: 'We have entered a new era of warfare, witnessing a destructive and deadly mix of conventional military might and malicious cyber attacks.

'Russia is ripping up the rule book by undermining democracy, wrecking livelihoods by targeting critical infrastructure, and weaponising information. We must be primed and ready to tackle these stark and intensifying threats.'

UK Defence Secretary Gavin Williamson accused Vladimir Putin of 'ripping up the rule book'

Foreign minister for cyber security Lord Ahmad of Wimbledon said the UK's decision to identify the Kremlin as responsible for the attack underlines the fact the Government will not tolerate 'malicious cyber activity'.

He said: 'The UK Government judges that the Russian government, specifically the Russian military, was responsible for the destructive NotPetya cyber attack of June 2017.

'The attack showed a continued disregard for Ukrainian sovereignty. Its reckless release disrupted organisations across Europe costing hundreds of millions of pounds.'

He added: 'The Kremlin has positioned Russia in direct opposition to the West yet it doesn't have to be that way. We call upon Russia to be the responsible member of the international community it claims to be rather then secretly trying to undermine it.

'The United Kingdom is identifying, pursuing and responding to malicious cyber activity regardless of where it originates, imposing costs on those who would seek to do us harm.

'We are committed to strengthening co-ordinated international efforts to uphold a free, open, peaceful and secure cyberspace.'

His comments point to UK intelligence agencies discovering evidence indicating the involvement of the Russian military.