Boko Haram militants are raping women to breed children they hope will bolster their numbers and carry on their ideology, according to reports.

The New York Times has spoken to women who have escaped the militant force in Nigeria, often carrying children in utero.

Hundreds of women and girls who have been captured and held in squalid rooms said they were selected for rape with the purpose of making them pregnant.

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Hamsatu, 25, said she was four months pregnant to a Boko Haram member after the militia took control of her town.

“They chose the ones they wanted to marry,” she said. “If anybody shouts, they said they would shoot them.”

As the militants have been forced out of the towns they occupied for about a year, battered and pregnant women in their dozens have streamed towards a displaced people’s camp near the Nigerian capital Maiduguri.

They tell their stories of being kept in a single room together and hearing the door open before another militant selects them for sexual violence.

The sect calls the process marriage. “We would marry them out at the age of 9,” the leader, Abubakar Shekau, said in a video message after nearly 300 girls were abducted from a village called Chibok.

A local official, governer Kashim Shetima said the leaders of the sect made efforts to make women pregnant.

“The sect leaders make a very conscious effort to impregnate the women,” Shettima said. “Some of them, I was told, even pray before mating, offering supplications for God to make the products of what they are doing become children that will inherit their ideology.”