Russian police have freed more than a dozen children who were being held in underground isolation by a Muslim sect in Kazan, in the eastern republic of Tartarstan.
Some of the 60 members of the religious group, followers of a local spiritual leader, had lived for more than a decade in a bunker below a mosque in the city, the police said.
The children had been forced to live in squalid conditions with no access to the outside world.
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The bunker was discovered in police searches of Islamic organizations in the city following twin attacks last month on moderate clerics.
"The children are living in unsanitary conditions. There is a lack of ventilation. The premises are like monks' cells," police investigator Ranis Bakhitov said.
"Based on the evidence of police officers, all the children require medical attention."
"During the search we found that the building was two story. Below it was a cellar where we found people were living," said Bakhitov in a video released by the local interior ministry.
"The space was built as a labyrinth. There are rooms measuring two by three meters," (six feet by 10), he said.
The police said they had established that around 60 people were living in the underground quarters, including 15 children.
The group's 85-year-old leader, Faizrakhman Satarov, declared himself a prophet in 1964, the ministry said.
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In 1996, Satarov acquired land for an Islamic school and built living quarters there where "gradually all the members of the sect moved to live permanently," police said.
"Faizrakhman's supporters lead a closed way of life, not leaving their shelter without extreme necessity," the ministry said.
"The children of the commune grew up in the same conditions. They did not go to educational and medical institutions, which is the most severe breach of children's rights."
Police said they had opened a criminal case against Satarov for his "arbitrariness" in running the compound, a crime that carries a prison term of up to six months.
They also opened separate investigations into members' failure to carry out their obligations as parents.
The attacks on July 19 targeted Tatarstan's chief Muslim cleric, Ildus Faizov, who survived a car bombing, while his one-time deputy was killed in a shooting.
A militant this month claimed the attack in a video posted online. Tatarstan is often held up as an example of religious tolerance.