Cairo: Yemen’s Al Houthi militants hold dozens of women without bringing them to trial or charging them with a crime, often torturing the detainees and blackmailing their families, activists said on Thursday.

The allegations were first raised over the weekend by the Yemen Organisation for Combating Human Trafficking, based in the capital, Sana’a.

The group’s founder, Nabil Fadel, told The Associated Press that he received information from families, former female detainees, and other sources showing that over the past months, Al Houthis have been rounding up women over allegations of prostitution and collaboration with the Saudi-led coalition, which is at war with the militants.

A Yemeni rights lawyer on Thursday told the AP the women were rounded up from cafes and parks the past months.

Speaking on condition of anonymity for fears for personal safety, he said their families are searching for their missing daughters.

The Yemeni anti-trafficking group said it obtained new information showing that the militants were carrying out atrocities such as “abuse, torture, and forced disappearances of women and girls in secret and illegal prisons.”

The militant leader, Abdul Malek Al Houthi, had recently warned in televised speeches about a so-called “soft war” against Al Houthis by their enemies, pointing to their “corrupt morals and sins.”

Fadel, of the anti-trafficking group, said the arrests started after the Al Houthi appointment a year ago of Sultan Zabin as head of the Sana’a criminal investigation division.

Zabin promptly launched a crackdown on prostitution and smuggling.

Women who had been rounded up in the crackdown and subsequently granted release were sent to secret detentions in villas across the Yemeni capital, instead of being set free.

An AP investigation last month showed that thousands of Yemenis have been imprisoned by the Al Houthi militia during the four years of Yemen’s grinding civil war.

Many of them suffered extreme torture—being smashed in their faces with batons, hung from chains by their wrists or genitals for weeks at a time, and scorched with acid.

The revelations about women detainees come as representatives of Yemen’s warring sides are in Jordan for talks on implementing a prisoners exchange deal agreed to in Sweden last month.

Yemen plunged into civil war in 2014, when the militants captured the capital, Sana’a.

A Saudi-led coalition intervened a year later—fighting alongside government troops—to restore the legitimate government.

In Sweden, the two sides agreed to confidence-building measures, including an exchange of thousands of prisoners. But the implementation of that has been slow marred by violence.