Georgia, Britain and the United States on Thursday accused Russia of orchestrating a "reckless" cyber assault against the pro-Western Caucasus nation last year as part of an aggressive campaign of online attacks worldwide.

Tbilisi and the transatlantic allies blamed the late October hacking of some 15,000 websites in the former Soviet republic on Russian military intelligence and vowed to step up efforts to counter Moscow's activity.

"Georgia condemns this cyber-attack, which goes against international norms and principles, once again infringing (on) Georgia's sovereignty in order to hinder the country's European and Euro-Atlantic integration and democratic development," Georgia's foreign ministry said in a statement.

The hack, which they said was carried out by Russia's GRU military intelligence, targeted the websites of the president, courts and media outlets, among others.

"The GRU's reckless and brazen campaign of cyber-attacks against Georgia, a sovereign and independent nation, is totally unacceptable," British Foreign Secretary Dominic Raab said in a statement.

"The Russian government has a clear choice: continue this aggressive pattern of behaviour against other countries, or become a responsible partner which respects international law."

Moscow has denied involvement.

Russian Deputy Foreign Minister Andrei Rudenko said that "Russia had not planned and is not planning to interfere in Georgia's internal affairs in any form."

The GRU has been linked to a series of major attacks, including the hacking of US Democratic National Committee (DNC) servers before President Donald Trump's election in 2016.

Last month, US cyber firm Area 1 Security said Russian operatives had hacked a Ukrainian energy company at the centre of Trump's impeachment trial.

Britain and its allies also allege GRU officers poisoned former Russian double agent Sergei Skripal in 2018. He survived but another person was killed by the poison.

The hack targeted the websites of Georgia's president, courts and media outlets, among others
The hack targeted the websites of Georgia's president, courts and media outlets, among others AFP / Fred TANNEAU

The British government said its National Cyber Security Centre had decided Moscow was behind the Georgia cyber attack "with the highest level of probability".

The US State Department said for its part the incident demonstrated "a continuing pattern of reckless Russian GRU cyber operations against a number of countries".

"The stability of cyberspace depends on the responsible behaviour of nations," the US statement said.

"We, together with the international community, will continue our efforts to uphold an international framework of responsible state behaviour in cyberspace."

The 2019 cyber attack on the Caucasus country on Russia's southern border resulted in some websites displaying a photo of Georgia's exiled former president Mikheil Saakashvili with the inscription: "I'll be back!"

Saakashvili turned into a sworn enemy of Moscow and later served as a regional governor in pro-Western Ukraine.

The attack also affected servers of Georgia's two major broadcasters, Maestro and Imedi TV, temporarily sending the television stations off the air.

In 2008, in the run-up to and during the war between Russia and Georgia, Tbilisi accused Moscow of an all-out cyber attack against the websites of nearly all government agencies and leading banks.

Russia denied the allegations at the time but said "individuals in Russia" might have been responsible.

Western analysts alleged Russia's security services had probably played a key role in organising the attacks.

In its condemnation on Thursday, the US said it would offer Georgia additional capacity building and technical assistance to help strengthen its public institutions and protect against further online attacks.

The brief but bloody 2008 war marked the culmination of tensions between the arch-foe countries over Georgia's bid to forge closer ties with the West, which has long angered Tbilisi's Soviet-era master Russia.