To locals in the Russian village of Nikolskoye they were simply a group of eccentric Christian believers. And when 29 members of the sect abruptly vanished last month, villagers assumed they had packed up and gone.
In fact, the religious doomsday cult had taken up residence in a remote underground cave. They had decided to barricade themselves inside until May 2008 - the date when their spiritual leader told them the world was going to end.
Today, authorities were attempting to talk to cult members by bellowing through a ventilation shaft cut into the cave's roof. So far, however, the members - who include 25 adults and four children, one of them a 16-month-old baby - have refused to emerge.
"They have covered the entrance and refuse to come out and are threatening to blow themselves up. They threaten to detonate a gas tank," an official in the local prosecutor's office said. "They say they are fine. They tell us to go away," another added.
The sect members are hiding out in a snow-covered hillside in the Penza region of central Russia, about 60 miles from the town of Penza.
The chief prosecutor of the region's Bekovsky district, Alvetina Volchkova, said they moved in at the end of October.
"I talked to them last Thursday," she told the Guardian today. "The temperature outside was freezing. They told me they were fine and that the temperature inside the cave was plus 17C. They've lit candles and paraffin lamps. I asked if I could come in and have a look around but they wouldn't let me in.
"They don't have a name as such. They don't regard themselves as a sect but refer to themselves as 'the chosen ones'. They also say that they are representatives of the Russian Orthodox Church."
The police had sealed off the area and were trying to negotiate, she added.
"No-one wants to take on the responsibility of provoking them ... because our information is that there are children among them,' a police spokeswoman told Reuters.
The cave is two miles from the modest tin-roofed prayer hall where sect members used to gather to sing songs. Elders began secretly preparing the cave last month - bringing in supplies of gas and kerosene, as well as half a tonne of honey and a lot of jam, locals said.
The sect's leader is Pyotr Kuznetsov - a divorced 43-year-old architect from Belarus. Kutnetsov travelled across Belarus and Russia, spreading his message of apocalyptic doom, before settling in the village 18 months ago, locals said.
Several dozen believers followed him. They moved into abandoned houses, refusing to use electricity. "They are simple Christians," a local priest, Father Georgy, told NTV television. "They say: 'The church is doing a bad job, the end of the world is coming soon and we are all saving ourselves.'"
After decades of state suppression, the Russian Orthodox Church is now enjoying a revival. But many Russians and ex-Soviet nationals have also fallen under the sway of local and foreign sects. Some even refuse passports and taxpayers' numbers, claiming the figures conceal "satanic" meanings.
However, the tradition of religious dissent in Russia and defiance of secular authority goes back much further. In the seventeenth century, one group, the Old Believers, founded their own church in protest at reforms to orthodox rituals. To escape persecution, many settled in extremely lonely communities.
The cave in Penza was discovered after the daughter of one of the missing cult members complained to the local prosecutor, Russian media said. Police then arrested Kuznetsov - who led investigators to the entrance. When they tried to approach together with another priest gunshots were fired in the air, NTV reported.
"Kuznetsov is their spiritual leader. He told them that the world would end in May and that the only way for them to save themselves was to go underground," Pavel Shishkin, a reporter with Komsomolskaya Pravda in Penza told the Guardian today. "They believed him. They've gone to sit it out."
Izvestiya newspaper yesterday reported that Kuznetsov suffered from schizophrenia and that in the last few months he had been sleeping in a coffin.
"He said his followers should not be disturbed, that they are the chosen ones, and that no one else is allowed to get in the cave," a law enforcement officer told the paper.
Police and ambulances have sealed off the approach to the cave, which is scarcely visible from the outside and hidden by a sloping ravine. Relatives of cult members are expected to arrive at the scene shortly from Belarus and Ukraine to try and persuade their loved ones to give up. This may be tricky, however, as cult members have apparently taken a vow of silence.
Asked whether Russian special forces would storm the cave, Volchkova said: "For the moment the police are making sure that the situation is OK and under control."
Prosecutors have opened a criminal investigation under article 235 of Russia's criminal code, against illegal religious societies, she added.