Alexander Shiplyuk is the third prominent Novosibirsk-based scientist to be taken into custody over the past few months.
Families of soldiers killed in Putin's war are being monitored incase they voice public opposition to the conflict, according to Kyiv intelligence.
The homes and workplaces of the three men were searched on Tuesday by employees of Russia's Federal Security Service.
A Moscow court ordered Dmitry Kolker be held in custody for two months pending an investigation by the Federal Security Service, even though he was gravely ill in hospital.
Multiple mysterious fires have been reported at government and military enlistment buildings across Russia since Vladimir Putin declared a full-scale invasion of Ukraine in February.
The claim contradicted Taiwan's own intelligence services, which said a move by Beijing wasn't likely in the near future.
The five men were arrested on November 28 in a forest near Vyborg, by Russia's border with Finland.
Alexander Bortnikov, head of the Federal Security Service, warned that 5,000 fighters from ISIS had been deployed in northern Afghanistan.
The men were captured during a violent confrontation with Russian navy ships on Sunday.
Angry anti-Russian demonstrators set fires and threw smoke bombs and flares outside the compound.
The bomber died and three employees were injured by the blast, which investigators are treating as an act of terrorism.
Meanwhile, Russia's Ministry of Economic Development has put forward amendments to federal law that would allow companies to hide information about some public contracts.
The U.S. government added three Russians and five companies said to be linked to Moscow's security forces.
The lobby group Victims of Communism says it was an attempt to promote a "revisionist history of the Soviet Union."
The app must share encryption keys to read users' messages or face a nationwide ban, Russian authorities said.
The police found three laboratories producing forged documents, seals and stamps to help people cross borders illegally.
The Kremlin may have ordered a hit on an ex-Russian spy in the U.K. But some point to a scarier prospect—that Moscow's death squads did it on their own.
Convicted Russian spy Sergei Skripal's "substance exposure" is drawing comparisons to the 2006 death of Russian intelligence agent Alexander Litvinenko's acute radiation poisoning.
The president also thanked his security services for keeping Russia's new generation of weapons secret.
A new poll shows an increase in popularity across the board for state security careers, but it may not all be down to the job itself.
Whatever the historical context, most of the Kremlin's agents "have always been true servants of the state and patriots," the former KGB officer said.
Authorities reportedly suspect the Russian national of handing state secrets about the country's Navy to the West.
Russia's security service posted images and video of an apartment they said served as a "laboratory" of arms for the detained extremists.
The drill will help authorities practice their response to a terrorist threat in the middle of Moscow.
The Russian leader wants the newly-established force to protect his regional allies too.