A court in Moscow has sentenced a researcher who worked for the city's prestigious USA-Canada Institute to 15 years in prison for espionage.
Sutyagin's trial is the latest in a series of cases against researchers
Weapons specialist Igor Sutyagin was convicted by a jury this week of passing information to a UK firm allegedly used as a front by the CIA.
Sutyagin's defence has protested his innocence, saying his work was all based on publicly available sources.
Correspondents say the case has shocked the Russian academic world.
Sutyagin's lawyers say they will appeal.
During the trial, prosecutors failed to establish Sutyagin had divulged state secrets.
Instead, he was convicted on Monday of passing information on submarines and missile warning systems to a UK firm.
Sutyagin, arrested in 1999, admitted selling information about Russian military hardware to the consultancy firm.
But he insisted that the information was readily available and that he had no reason to believe he was dealing with a company used as an intelligence cover.
"I absolutely do not consider myself guilty, as I took all information... from newspapers and magazines" he told Russian Itar-Tass news agency after his sentencing.
The BBC's Steve Rosenberg reports from Moscow that the verdict may unnerve many Russian researchers and scientists who offer consultancy services to western companies as a means to bolster their meagre salaries.
The US State Department questioned the fairness of the closed-door trial, referring to its "lack of transparency and due process".
The case has also been condemned by human rights activists in Russia and abroad.
Four international rights groups protested to the Council of Europe in January that Sutyagin was "the target of politically-motivated treason charges".
After Monday's guilty verdict, Human Rights Watch spokesman Alexander Petrov told Reuters news agency the irregularities in Sutyagin's trial made it clear it had been "ordered at the behest of someone, namely the FSB" - after another researcher was acquitted in December.
The trial is one of a series of recent high-profile spy cases against Russian researchers:
Sutyagin - whose 15-year prison term is to be counted when he was detained - has 10 days to appeal against the sentence to the Supreme Court.
- Valentin Danilov was cleared of spying for China in December
Military reporter Grigory Pasko was released in January 2003 after serving two years for treason after disclosing how Russia had dumped nuclear waste in the Pacific Ocean
Alexander Nikitin, an environmentalist, was acquitted in 1999 of treason after contributing to a Norwegian report on radioactive pollution in the Arctic seas