Pyotr Kuznetsov, self-declared prophet, predicts that the end of the world will come this spring, so he sent his followers underground to wait for the doomsday.
On Friday, psychologists were negotiating with the doomsday cult members, who have sealed themselves in what officials described as a cave or a bunker in a snowy forest near the Volga River, threatening to blow themselves up if authorities intervene.
Stocked with food supplies and canisters of gasoline, the 29 people were waiting for the end of the world in the structure near Nikolskoye, a village in Penza region about 650 kilometers (400 miles) southeast of Moscow, regional spokesman Yevgeny Guseynov said.
"Any forceful action is dangerous," Guseynov said, but he said doctors and rescuers were near the structure's entrance and were trying to coax the cult members to leave.
The 29 people - including four children, one only 18 months old - were stocked with food and other supplies, including 400 liters (100 gallons) of gasoline they said they would ignite if authorities forced them out.
Kuznetsov - who did not himself join his followers in the cave - was undergoing psychiatric evaluation Friday, a day after he was charged with setting up a religious organization associated with violence, Guseynov said.
Kuznetsov established the so-called True Russian Orthodox Church after he split with the official Church, the regional official said.
On Thursday, black-clad Russian Orthodox monks carefully scaled down the snow-covered gully to try to make contact with the cult, but members refused to speak with clergy. They were exchanging letters with Kuznetsov, however, and were in contact with doctors and officials, who promised food or medical supplies if needed.
Kuznetsov blessed his followers before sending them into the cave earlier this month. Most of the adults were women, Russian newspaper Izvestia reported.
Kuznetsov, 43, a trained engineer who comes from a deeply religious family, declared himself a prophet several years ago, left his family and settled in Nikolskoye.
He began writing books, borrowing from a mixture of established beliefs, and visited monasteries both in Russia and Belarus, recruiting followers, Guseynov said.
Kuznetsov said his group believed that, in the afterlife, they would be judging whether others deserved heaven or hell, Izvestia reported Friday. Followers of his group were not allowed to watch television, listen to the radio or handle money, media reports said.
Russian Orthodox Church spokesman Georgy Ryabov said the emergence of Kuznetsov's cult was a consequence of "the absence of a system of spiritual and moral education" in Russia.
"All Christians of Russia have to pray for them so they awaken and understand their mistake," Ryabov said.
Russian President Vladimir Putin would never fall to the level of personal insults, Kremlin official spokesman Dmitry Peskov said