Two former cyber-security experts at Russia's FSB intelligence agency and another at a software firm have been charged with treason, a lawyer says.
Ex-FSB men Sergei Mikhailov and Dmitry Dokuchayev, and an executive at the anti-virus software firm Kaspersky, Ruslan Stoyanov, are accused of working for US interests.
Some reports suggested the arrests could be linked to claims of Russian hacking during the US election.
The Kremlin denied the claim.
The names of those charged were given by Ivan Pavlov, a lawyer acting for one of the men.
Russian media reports suggest Mr Mikhailov, who was formerly deputy head of the FSB's cyber-security department, was detained in dramatic style and led out of a meeting with a bag over his head.
As with all treason cases, details of these accusations have not been made public.
But the BBC's Sarah Rainsford in Moscow says claims from anonymous sources continue to circulate around the Russian capital, including one that links the arrests to a Russian server-renting firm accused of involvement in the hacking of voting systems in two US states.
President Vladimir Putin's spokesman, Dmitry Peskov, said the arrests were not related to the hacking, which Russia denies involvement in.
Other claims suggest that the men had links to a hacking group known as Shaltai Boltai (Humpty Dumpty), best known for digging dirt on senior Russian political figures and making it public.
Source: Radio Television Brunei