The Russian Federal Security Service (FSB) has detained a Russian armed forces serviceman and his brother in Smolensk and Pskov on suspicion of passing classified information to Estonian special services, Interfax news agency reported.
An investigation into alleged treason has been opened.
"The Federal Security Service of the Russian Federation in the cities of Smolensk and Pskov detained a serviceman of the Russian armed forces and his brother, who permanently resides in Estonia, on suspicion of gathering information constituting a state secret and passing it to Estonian special services," the FSB press center told Interfax.
FSB investigators have opened a criminal case on a count of treason.
The charge carries a punishment of 12 to 20 years in prison and a fine of 500,000 rubles (€5,400).
Spokespeople for Estonia's Foreign Intelligence Service told BNS on Tuesday that they will not comment on the topic.
A spokesman for the Internal Security Service (ISS), Harrys Puusepp, told BNS that in general, the ISS will comment on matters of counter-intelligence, one of its main duties, when a person acting in the interests of a special service of a foreign country has been detained as part of a criminal proceeding or an overview of one's work is offered in the annual review.
"The present is neither of these situations," he said.
Editor: Helen Wright