Russian police have freed more than a dozen children held for years in underground isolation by a Muslim sect in Kazan, in the eastern republic of Tartarstan, the Interior Ministry said.

Some 60 members of a 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.

At least 15 children who were part of the group had been forced to live in squalid conditions with no access to the outside world. The bunker was discovered in police searches of Islamic organisations in the city following twin attacks last month on moderate clerics by suspected Islamists.

Tatarstan President Rustam Minnikhanov said in a statement that 19 children, most aged under six and including three babies, had been rehoused in shelters following the raid.

And the same statement quoted members of the sect as saying there may be as many as 27 children.

A police video of the raid shown to reporters showed bearded male residents shouting as investigators forced their way inside the two-storey building. Women wearing headscarves were shown carrying young children, including babies, up a long flight of stairs from underground.

Police investigator Ranis Bakhitov said the children were “living in unsanitary conditions. There is a lack of ventilation. The premises are like monks’ cells. Based on the evidence of police officers, all the children require medical attention. During the search we found that the building was two-storey. Below it was a cellar where we found people were living,” said Mr Bakhitov in the video released by the local interior ministry.