Georgia said Friday it had dismantled a major spy ring for Russia and arrested 13 suspects including four Russian citizens, outraging Moscow two years after the ex-Soviet foes fought a brief war. Georgian interior ministry spokesman Shota Utiashvili said the suspects, who included Georgian military officers, had been providing secret information on Georgia's military to the Russian military's foreign intelligence service, the GRU. He said the ring had been smashed in a cloak-and-dagger operation that saw Georgian security services infiltrate the GRU through a former Soviet army officer working as a double agent and top secret Russian military codes broken. 'This is a huge deal in terms of Georgia securing its military intelligence and a big blow to the GRU,' Utiashvili told selfnews. Georgia and Russia fought a brief war in August 2008 that saw Russian forces pour into the country to repel a Georgian military attempt to retake the Moscow- backed rebel region of South Ossetia. Russia immediately denounced the arrests, which Georgia conspicuously chose to announce on the annual day in Russia celebrating the country's military intelligence service. The Russian foreign ministry said in a statement that the arrests showed Georgian President Mikheil Saakashvili was suffering from 'chronic spy-mania' motivated by 'anti-Russian' sentiments. 'The timing of this provocation is not an accident on the eve of a number of important events,' it said, referring to the NATO summit in Lisbon on November 19-20 to be attended by Russian President Dmitry Medvedev. Earlier, a foreign ministry source told the Interfax news agency that Russia was 'deeply angered' by the arrests and that they showed 'another worsening of the anti-Russian psychosis of the Georgian leadership'. Tensions between the two neighbours had been growing for years in the run-up to the war, including after the 2006 arrest of four Russian military officers on espionage charges. The four were eventually released and returned to Russia. In a statement, the interior ministry said it had conducted 'a major operation which uncovered several dozen people working covertly' for the GRU and listed the 13 people charged with espionage as a result of the investigation. It said Georgian security services had 'implanted a former Soviet Army officer into the GRU' who was able to obtain computer hardware and software that allowed Tbilisi to decipher GRU encryption codes and expose the spy ring. Of the nine Georgian citizens, six were military pilots who allegedly provided secret information to the GRU on the strength of Georgian military resources, including personnel and equipment, on combat readiness and on deployments. The others were a navy sailor who had provided radio call signs, and two civilians. Of the four Russian citizens, one was a GRU liaison officer responsible for sending information to Moscow, the ministry said. Two others were employees of a port inspection company, Saybolt Georgia, who allegedly provided information on foreign arms shipments to Georgia, and one was a local businessman who had carried out surveillance on individuals. Two other detained suspects had been released under a plea-bargain agreement, the ministry said. Utiashvili said the spy ring was centred on Georgia's Black Sea region of Adjara, a former Moscow-backed rebel province that Tbilisi regained control of in 2004. He said it had been operating since before the 2008 war and that the arrests had taken place over the last year. Utiashvili said the Georgian operative in the GRU had worked in Russia but was currently in Georgia. The operative had obtained 'encryption, decryption and security codes' that are regularly used by the GRU, Utiashvili said. 'The most important thing is their cryptographic system... because their codes and cipher system are now at Georgia's disposal,' he said. He said all the suspects, including the Russian citizens, would face trial in Georgia. Asked about the possibility of handing the Russian citizens over to Moscow, Utiashvili said: 'We have not received such a request from anybody.' 