Estonia has detained a man suspected of being a Russian agent operating against the Estonian state, the Prosecutor-General's Office says.
The man, a Russian citizen, was suspected of plotting a computer-related crime, among other things, prosecutor Inna Ombler said on November 7.
She said that Estonian state institutions were targeted but did not disclose details, adding that the suspect's detention last week means that "bigger damage was prevented."
Ombler said the suspect was working for the Russian Federal Security Service (FSB), the main successor to the Soviet-era KGB. The suspect, who was not identified, was formally charged in a Tallinn court on November 6.
In 2015 and 2016, three men in Estonia were convicted of cooperating with Russian intelligence services and sentenced to prison.
In May, Estonia expelled two Russian diplomats posted at Moscow's consulate in Narva over contacts with local officials that were considered inappropriate for diplomats.
Government and private Internet sites in Estonia suffered major cyberattacks in 2007, following a decision by the Baltic nation to move a Soviet-era war memorial from a square in the capital.
The small Baltic country has made cybersecurity a focus of its six-month EU presidency, which ends on December 31, following a series of global cyberattacks this year.
Occupied by the Soviet Union during World War II, Estonia gained independence in the Soviet collapse of 1991 and is now a member of NATO and the European Union.
Relations with Russia are severely strained.