Sipachev had admitted working for the Pentagon, the court said
A Moscow court has sentenced a Russian national to four years in prison for handing over state secrets to the US.
Gennady Sipachev was found guilty of sending classified Russian military maps to the Pentagon via the internet.
The maps can be used to make the targeting of US cruise missiles against Russian targets more accurate, Russia's security service officials said.
The court said that Sipachev had made a guilty plea bargain with prosecutors in exchange for a lighter sentence.
"Sipachev co-operated actively in the detection and investigation and also pointed to criminal activity by other individuals which helped prevent further damage to the security of Russia," said the court's ruling.
US silent
Sipachev was found guilty under Article 275 of Russia's criminal code - "state treason in the form of espionage". The charge normally carries a sentence of up to 20 years in prison.
The court said that Sipachev - whose age and occupation have not been disclosed - would be serving his sentence in a high-security prison.
Russia's security services (FSB) said Sipachev had first raised their suspicions in 2008.
The FSB said it later found that he had been sending top secret Russian military maps to a Pentagon's in-house intelligence service, which acted under the cover of a different organisation.
There has been no comment from the US on the issue.
A Russian citizen identified as Gennady Sipachyov has been convicted of "state treason in the form of espionage" and was sentenced to four years in a Russian maximum-security prison.

According to the Russian intelligence agency Federal Security Service (FSB), Sipachyov was found guilty of giving the American government classified military maps, which can be used to target American missiles against targets in Russia more accurately.  According to the FSB, the exchange of of information occurred in 2008, when Sipachyov emailed the documents to an organization called "East View Cartography," which was a cover for the intelligence service of the US military.

In its verdict, the court said that "The Pentagon required the maps in order to correct its guidance system for cruise missiles to increase the accuracy of targeting."  While no motive was identified, and the trial was barred to the media, speculation has been that any motive involved was financial in nature.

Sipachyov, whose age and profession were not released, was convicted under Article 275 of Russia's criminal code, pertaining to "state treason in the form of espionage."  Such a conviction ordinarily carries a sentence of 20 years, but according to the FSB, Sipachyov had "co-operated actively in the detection and investigation and also pointed to criminal activity by other individuals which helped prevent further damage to the security of Russia," leading to his sentence being reduced.

The incident has been seen as embarrassing for both the Russian and American governments, as the two countries are currently trying to repair their previously rocky relationship.  Earlier this year, a treaty reducing the number of nuclear weapons each country held was signed.  The US government has not commented on the ruling.