Russia is allegedly taking saliva samples from religiously conservative Muslim women to help its security forces identify remnants of suicide bombers in case of an attack sabotaging the Sochi Winter Olympics, Reuters news agency has reported, quoting locals in the North Caucasus.
The meassure came after a female blew herself up on a bus in Volgograd, a major city north of Sochi, on October 21 killing at least six people.
Dubbed "black widows", about 49 female suicide bombers have carried out attacks in Russia in the past 13 years, according to the Caucasian Knot website, which tracks the unrest.
In response, security forces have blown up the homes of attackers' relatives, sealed off mountain villages and rounded up young men suspected of having ties to armed fighters.
Critics say authorities are feeding the resentment that lies behind rebel attacks in the North Caucasus region.
"Allah does not allow us to take up arms. If he allowed it, we would," Albina Magomedova, a Salafi woman from Dagestan, told Reuters.
But other women said revenge attacks by women were allowed under Islam.
In July, Doku Umarov, the leader of Russia's rebel fighters, urged his armed men to use "maximum force" to
sabotage the Olympics.
"By the Olympics, the most important thing for our image is for the situation to be calm and normal in Dagestan," said Ramazan Dzhafarov, Dagestan's deputy prime minister.
President Vladimir Putin, who believes the $50bn Winter Olympics will bring prestige to Russia, tightened the courtry's security to prevent any attacks.
Vladimir Kolokoltsev, Russia's interior minister, told parliament that authorities were receiving "alarming information and were working to eliminate leaders and members of armed groups".
"There are simply no other ways to combat these inhuman monsters," Kolokoltsev said.
Security analysts say armed fighters are unlikely to penetrate the layers of protection around Sochi, but attacks cannot be ruled out, especially in nearby cities like Volgograd.