Witnesses alleged to the Associated Press that Yemeni guards working under the direction of Emirati officers use various methods of sexual torture and humiliation, including the filmed rape and assault of detainees.
The torturers followed a schedule.
Beatings on Saturdays, torture on Sundays, and Monday was a break. The next three days were the same routine.
On Fridays, it was time for solitary confinement.
From inside a Yemeni prison controlled by the United Arab Emirates – a top US ally – a Yemeni detainee held without charges chronicled alleged torture and sexual abuse through drawings.
Smuggled to The Associated Press from the Beir Ahmed prison in the southern city of Aden, the drawings appear to offer a grim glimpse into a hidden world of flagrant human rights abuses by UAE officers acting with impunity.
Sexual violence is a primary tool aimed at brutalising the detainees and extracting "confessions," the artist and six other detainees told AP.
The drawings – made on plastic plates – show a man hanging naked from chains while he is being subjected to electric shocks, another inmate on the floor surrounded by snarling dogs as several people kick him, and graphic depictions of rape.
"The worst thing about it is that I wish for death every day and I can't find it," the artist said, summing up nearly two years in detention that started last year after he spoke against the Emiratis in public.
The UAE's alleged secret prisons and widespread torture were detailed in an AP investigation last June.
The AP says it has since identified at least five prisons where security forces use sexual torture to brutalise and break inmates.
TRT World's Nafisa Latic has more.
Yemen's war began in 2015, after Iranian-backed Houthi rebels took over much of the country's north.
Saudi Arabia and the UAE are leading a coalition to fight the rebels, but UAE forces have overtaken wide swathes of territory, towns and cities in the south.
The US is backing the coalition with billions of dollars in arms, and partners with the Emiratis in anti-terrorism campaigns.
Emiratis have swept up hundreds of Yemeni men on suspicion of being Al Qaeda or Daesh militants. The prisoners are held in at least 18 hidden prisons, apparently without charges or trials.
Witnesses said Yemeni guards working under the direction of Emirati officers use various methods of sexual torture and humiliation. They said the officers rape detainees while filming the assaults.
"They strip you naked, then tie your hands to a steel pole from the right and the left so you are spread open in front of them. Then sodomising starts," said one father of four who say he has been in detention for more than two years and who, like other detainees, spoke to AP on condition of anonymity for fear of retaliation.
A former security chief who was allegedly involved in torturing to extract confessions told AP that rape is used as a way to force detainees to co-operate with the Emiratis in spying.
"In some cases, they rape the detainee, film him while raping, use it as a way to force him to work for them," he said, speaking on condition of anonymity because of concerns for his safety.
The official has since defected from the Emirates and fled the country.
US says no knowledge of abuse
American officials confirmed last year that the US has interrogated some detainees at the secret prisons run by the UAE.
The Pentagon has insisted that it had no knowledge of human rights abuses. Obtaining intelligence extracted by torture would violate international law.
The AP first asked the Pentagon about grave rights abuses committed by the UAE, its partner, one year ago.
But despite well-documented reports of alleged UAE involvement in torture by the AP, human rights groups and even the United Nations, Marine Major Adrian Rankine-Galloway, a Pentagon spokesman, said that the US has seen no evidence of detainee abuse in Yemen.
Still, he called the allegations "disturbing" and said, "The United States takes all allegations of abuse seriously, although we have no substantiating information at this time."
On May 24, the House of Representatives voted to require Defense Secretary Jim Mattis to investigate the scope of US involvement in UAE black sites.
The language, which would still need to pass the Senate, would require the Defense Department to submit a report within 120 days to Congress.
Reacting to AP's report, the State Department called the allegations "disturbing" and called on the UAE to investigate.
UAE denies accusations
UAE officials did not respond to requests for comment, but the country's permanent mission to the United Nations in Geneva released a statement after publication.
"The UAE has never managed or run prisons or secret detention centres in Yemen," the mission said.
But Yemen's interior minister has said he does not have authority over prisons and must ask for UAE permission to enter Aden.
Of five prisons where the AP says it found sexual torture, four are in Aden, according to three Yemeni security and military officials who spoke on condition of anonymity because they feared retalitation.
One is at Aden's Buriqa base – the headquarters for the Emirati forces and where US officers were seen along with Colombian mercenaries, according to two prisoners and two security officials.
Inside, prisoners said that American personnel in uniform weren't directly involved but were aware of the alleged torture – either by hearing the screams or seeing the marks.
"Americans use Emiratis as gloves to do their dirty work," said one senior security official at the Riyan prison in Mukalla, who spoke on condition of anonymity because of security concerns.
"Joining ISIS [Daesh] and Al Qaeda became a way to take revenge for all the sexual abuses and sodomy," said a top Yemeni commander currently in Riyadh, referring to the Emiratis.
He used an alternate acronym for Daesh and spoke on condition of anonymity for fear of retaliation.