Human Rights Watch on Tuesday accused Yemen's Huthi rebels of hostage-taking, torture and other serious abuses against people in their custody.
The New York-based watchdog said it had documented 16 cases of illegal imprisonment by the Iran-backed Shiite insurgents, "in large part to extort money from relatives or to exchange them for people held by opposing forces".
"Huthi officials have treated detainees brutally, often amounting to torture," HRW said, adding that former detainees described being beaten with iron rods, wooden sticks and assault rifles.
Prisoners were shackled to walls, caned and threatened with rape, it said, noting that hostage-taking "is a serious violation of the laws of war and a war crime".
"The Huthis have added profiteering to their long list of abuses and offences against the people under their control in Yemen," said HRW Middle East director Sarah Leah Whitson.
"Rather than treat detainees humanely, some Huthi officials are exploiting their power to turn a profit through detention, torture and murder."
The Huthis seized the capital Sanaa in 2014, forcing the government of President Abedrabbo Mansour Hadi to flee south.
Nearly 10,000 people, mostly civilians, have been killed since a coalition led by Saudi Arabia and the United Arab Emirates intervened on the side of the Yemeni government in 2015.
UN investigators said last month that all sides in the conflict may have committed war crimes, pointing to widespread arbitrary detention, rape, torture and the recruitment of children.
HRW called on the UN Human Rights Council to renew the mandate of a group of experts on Yemen to investigate and identify all parties responsible for abuses.
"The United Arab Emirates, UAE proxies, and Yemeni government forces have also arbitrarily detained, tortured and forcibly disappeared scores of people in the Yemeni conflict," it said.
© 2018 AFP