The Moscow Military District Court sentenced on Wednesday retired Federal Security Service (FSB) Colonel Valery Mikhailov to 18 years in a high-security prison for spying for the United States.
The verdict, which was announced behind closed doors, said Mikhailov had also been fined 500,000 rubles (about $15,300), stripped of his rank and state awards, and his property in Ukraine was also seized.
According to the investigation, Mikhailov contacted CIA intelligence officers in Moscow on his own initiative while serving in the FSB and passed state secrets to them.
The details of the case have not been disclosed due to the highly-classified nature of the information.
Prosecutors demanded 13 years and four months in jail, a fine and seizure of property for Mikhailov while his defense asked for six years in jail without property seizure.
