MOSCOW -- A self-proclaimed prophet had a vision from God: He would build an Islamic caliphate under the earth.

The digging began and 70 followers soon moved into an 8-story honeycomb of cramped cells with no light, heating or ventilation.

Children were born. They, too, lived in the cold underground cells. Until authorities raided the compound last week and freed the 27 sons and daughters of the sect -- who rarely saw the light of day.

Aged between 1 and 17, the children had never left the property, attended school or been seen by a doctor, officials said Wednesday. Their parents were charged with child abuse.

The sect's 83-year-old founder, Faizrakhman Satarov, who declared himself a prophet in contradiction with the principles of Islam, has also been charged with negligence, said Irina Petrova, deputy prosecutor in the provincial capital of Kazan.

No members of the sect, who call themselves "muammin" after the Arabic term that means "believers," have been arrested, she said. Under Russian law, child abuse charges do not necessarily lead to arrest or a prison sentence.

The children were discovered last week when police searched the sect grounds as part of an investigation into the recent killing of a top Tatarstan Muslim cleric, an attack local officials blame on radical Islamist groups that have mushroomed in the oil-rich, Volga River province of Tatarstan.

Satarov, a former top imam in the neighbouring province of Bashkortostan, ordered some 70 followers to live in cells they dug under the three-story building topped by a small minaret with a tin crescent moon. Only a few sect members were allowed to leave the premises to work as traders at a local market, Russian media reported.

The children were examined in local hospitals and will temporarily live in an orphanage, pediatrician Tatyana Moroz said. "They looked nourished, but dirty, so we had to wash them," she said in televised remarks.

Their parents voiced concern about the children's medical treatment.

Doctors "can do anything to them," Fana Sayanova, a woman with a veiled face and clad in a long white dress, told local television.

The cramped cells, without ventilation, heating or a regular electricity supply, form eight levels under the decrepit three-story brick house on a 700-square-metre plot of land. The house was built illegally and will be demolished, Tatarstan police told local media.

"They will come with bulldozers and guns, but they will have to demolish this house over our dead bodies!" sect member Gumer Ganiyev said on the Vesti television channel. The ailing Satarov appointed Ganiyev as his deputy "prophet," according to local media.

Satarov had followers in several other cities in Tatarstan and other Volga River provinces, local media reported.

In a 2008 interview with the Komsomolskaya Pravda daily, Satarov said that he fell out with other clerics and authorities in the Communist era, when he said the KGB sent him to Muslim nations with stories about religious freedom in the officially atheist Soviet Union. Government-approved Orthodox Christian, Muslim and Jewish clerics routinely travelled abroad on Soviet publicity trips.

"That's how I became Satan's servant, a traitor," the white-bearded and turbaned man was quoted as saying. "When I understood that, I repented and started preaching."

Muslim leaders in Tatarstan said Satarov's views contradict their dogma.

"Islam postulates that there are no other prophets after Mohammad," Kazan-based theologian Rais Suleimanov told the Gazeta.ru online publication Tuesday. "The teachings of Sattarov, who declared himself a prophet, have been rejected by traditional Muslims."

The sect members stopped accepting new members and are "only dangerous to themselves and their children," Suleimanov was quoted as saying.

Police raided Satarov's house last Friday as part of an ongoing investigation into the killing of Valiulla Yakupov, Tatarstan's deputy chief mufti, who was gunned down in mid-July as he left his house in Kazan. Minutes later, chief mufti Ildus Faizov was wounded in the legs after an explosive device ripped through his car in central Kazan.

Both clerics were known as critics of radical Islamist groups that advocate a strict and puritan version of Islam known as Salafism.

The emergence of Salafist groups in Tatarstan and other Volga River provinces with a sizable Muslim population has been fueled by the influx of jihadists and clerics from Chechnya and other provinces of Russia's Caucasus region, where Islamic insurgency has been raging for years.

Last year, Doku Umarov, the leader of the embattled Chechen separatists, issued a religious decree calling on radical Islamists from the Caucasus to move to the densely-populated Volga River region that includes Tatarstan.

Prosecutors have named two suspects in the cleric's killing who remain at large and arrested five others in the case. Islamist youth groups have staged rallies in Kazan demanding the detainees' release.

More than half of Tatarstan's 4 million people are Sunni Muslims. Tatars converted to Islam more than a thousand years ago, and the province became an important centre of Muslim learning and culture under Tatar-Mongol rulers who controlled Russia and parts of Eastern Europe.

Islamic radicals from the Caucasus have called for the establishment of a caliphate, an independent Islamic state under Shariah law that includes the Caucasus, Tatarstan and other parts of Russia that were once part of the Golden Horde -- a medieval Muslim state ruled by a Tatar-Mongol dynasty.