Russia's federal security service should abandon the spate of espionage cases it has brought against academics and scientists, human rights activists have demanded.
The Moscow Helsinki Group, the Ecology and Human Rights Group and lawyers representing university researchers accused of selling secrets to foreign powers urged the FSB - successor to the Soviet-era KGB - to stop abusing draconian laws to go after researchers working on contracts with foreign firms or universities.
Ludmila Alexeyeva, chairwoman of the Moscow Helsinki Group, told a press conference: "There is a fashion for arresting scientists accused of spying or leaking state secrets. It is unprofessional, but it is done to show that the FSB is doing something."
In a wave of espionage cases initiated by the FSB over the past few years, four scientists have been accused of selling secrets to foreigners. Among them is Igor Sutyagin, a researcher from Moscow's USA and Canada Institute who has spent four years in prison.
Mr Sutyagin was arrested in 1999, accused of passing military secrets to a British company that was allegedly a front for the US Central Intelligence Agency.
Campaigners for his release described the case as a farce and said the FSB had not produced a shred of evidence that Mr Sutyagin, whose field is arms control, had access to anything other than newspaper reports of long-declassified information.
Valentin Danilov, a physicist from Krasnoyarsk State Technical University who was accused of selling space technology to the Chinese, urged the authorities to release Mr Sutyagin.
"I spent 19 months in prison before my release last year," Dr Danilov said.
"Igor Sutyagin has been in prison for four years. There is no reason for him to be in jail, and he should be allowed out immediately to continue his very important work."
Last week, the supreme court ordered a regional court to rule in Professor Danilov's case, overturning an earlier ruling that allowed prosecutors to clarify the charges.
Leading members of the Russian Academy of Sciences have signed affidavits in both Professor Danilov's and Mr Sutyagin's cases stating that neither's work involved state secrets.
Ernst Chyorny, chairman of the Moscow-based Ecology and Human Rights Group, compared the situation in Russia with the 1930s and said that the FSB's power had increased dramatically under President Vladimir Putin. "The FSB has no basis for its cases against these scientists, but sadly today it does not answer to the law or the courts."
Pavel Podvig, an arms-control researcher based at Princeton University who has worked closely with Mr Sutyagin, said: "I am sure that public opinion has made a difference. There are signs that the FSB is afraid of Sutyagin's trial," he said.
Mr Sutyagin's trial was scheduled for August or September, he said. The defence has demanded a jury trial because it has "serious doubts about the impartiality of the Moscow court".