(CNN) -- Georgia has arrested 15 people who allegedly spied for Russia, including six pilots in the Georgian Air Forces, Georgian authorities said Friday.
Russia called the Georgian claims a "political farce."
Two of the 15 have since been released under plea bargain agreements, but the rest are still being held, the Georgian Ministry of Internal Affairs said. Ten are charged with espionage and three are charged with working for a special service of a foreign country, it said.
Georgia said it discovered "several dozens" of people who were covertly working in Georgia for the Main Intelligence Division of the Russian Ministry of Defense.
It then "implanted" a former Soviet Army officer into the Russian intelligence division, where he gained their trust in order to glean information, Georgia said.
"In order to carry out espionage activities, Russians gave him special computer hardware and software for encrypting the exchanged information," the Georgian Ministry of Internal Affairs said. "This person handed over both the hardware and the software to the counter-intelligence department of the MIA of Georgia, thereby making it possible to identify their functioning mechanisms."
The 13 people who have now been charged include nine Georgian citizens: the six pilots, two businessmen, and a sailor and radio specialist. The other four are Russian citizens, including three businessmen and a liaison officer for the Russian Main Intelligence Division, Georgia said.
Russia's Deputy Foreign Minister Grigory Karasin told the RIA Novosti news agency that the Georgian claims are a "political farce."
"Let's wait and see how much convincing will this political farce be to give our comments then," he said.
The Interfax news agency quoted an unnamed Russian security service source as saying the arrests are a provocation by Georgia.
Cross-border tensions between Russia and Georgia erupted into a five-day conflict in 2008, after Georgia launched a campaign against South Ossetia, a breakaway Georgian territory that borders Russia.
The following day, Russian tanks, troops, and armored vehicles poured into both South Ossetia and another breakaway territory, Abkhazia, and soon advanced into Georgian cities outside the rebel regions.
A total of about 850 people were killed on all sides and an unknown number of others were wounded or left missing, a European Union fact-finding mission concluded last year.
Russia and Georgia each blamed the other for starting the conflict, though the EU mission said it was rooted in a "profusion" of causes.
Moscow has since recognized South Ossetia and Abkhazia as independent regions.