The Russian citizen is suspected of non-violent activities against the Republic of Estonia and the preparation of computer-related crime.

The targets in his activities against Estonia were Estonian state agencies.

According to State Prosecutor Inna Ombler, who is leading the criminal investigation, allegations of crimes against the state are serious.

"Acting against the Republic of Estonia as an agent of the special service of a foreign country is without a doubt a serious crime, and we will figure out all the essential facts as soon as possible," Ombler confirmed.

"Right now, we can say without releasing any details that greater damage was prevented," she added.

Ombler also confirmed to ERR's radio news on Tuesday that there are currently no other suspects in this investigation.

The criminal investigation launched regarding the matter will be led by the Office of the Prosecutor General and conducted by the Estonian Internal Security Service.

Russian Embassy: We have been notified of arrest

Estonian authorities have notified the Russian Embassy in Estonia of the detention of the Russian citizen.

"The Office of the Prosecutor General on Nov. 7 officially informed the Russian Embassy in Tallinn that a 20-year-old Russian citizen was arrested on Nov. 4 while attempting to travel to Russia," the embassy said on social media on Tuesday.

"By a Nov. 6 decision of Harju County Court, he was taken into custody," the embassy continued, noting that a criminal investigation had been launched against the man based on paragraphs 233 and 216 of Estonia's Penal Code.

"Russia's diplomatic institutions are keeping a close eye on the development of the situation," the embassy said. "Our consuls are ready to provide assistance to the Russian citizen when a request from him to this effect is received."