SANNA:- An international rights group is calling for an investigation into alleged disappearances, torture and likely deaths in prisons and "network of secret detention facilities" run by the United Arab Emiratesinfo-icon and allied militias in southern Yemeninfo-icon.

Amnesty Internationalinfo-icon said in a report on Thursday that it has documented "systemic enforced disappearance and torture and other ill-treatment, amounting to warinfo-icon crimes" in the facilities.

The report said "some (detainees are) feared to have died in custody".

What USinfo-icon and UKinfo-icon mediainfo-icon won't tell you about the war in Yemen

Based on more than 70 interviews, the authors said "cruel and unlawful" practices were being committed in those prisons.

Amnesty called on the UAEinfo-icon government to immediately stop the torture, and to release detainees.

In the meantime, it said the US should suspend intelligence gathering cooperation with the UAE, and stop supplying it with weaponsinfo-icon.

Amnesty said that the 51 cases of enforced disappearance took place between March 2016 and May 2018.

Nineteen of the men remain missing, it said.

Amnesty said it had collected testimonies from released detainees and relatives of the missing across Yemen.

"We've done this through interviews with families, government officials, current and former detainess," Tirana Hasson, director for crisis response at Amnesty, said in an interviewinfo-icon with Al Jazeera. 

"We've also been on the ground in Aden ... and all fingers point to really alarming patterns of abuseinfo-icon that have been ongoing now for well over a year, and they have been taking place within a culture of impunity."

The "most egregious violations" were committed in the "network of secret detention facilities" maintained by the UAE, Tirana said.

One former detainee told Amnesty that "UAE soldiers at a coalition base in Aden repeatedly inserted an object into his anus until he bled" and that he was "kept in a hole in the ground with only his head above the surface and left to defecate and urinate on himself in that position".

Last year, the Associated Press news agency reported that the UAE and its allied militias were running a network of secret detention facilities, beyond the control of the Yemeni government.

The UAE has played a key role in the Saudi-led military operation in Yemen since 2015 [AP]

In June, the AP revealed that hundreds of detainees had been subjected to sexual abuse and torture.

On Wednesday, Yemen called on the UAE to close the informal prisons.

The UAE has denied involvement in prisons across southern Yemen.

On Monday, Reem al-Hashimi, the UAE minister for international cooperation, met Yemen's President Abd-Rabbu Mansour Hadi and Interior Minister Ahmed al-Maysari, who "insisted on the need to close the prisons and place them under judicial control", according to Yemeni state media.

The Gulf state has played a key role in a Saudi-led military operation since 2015 to bolster Yemen's President Abd-Rabbu Mansour Hadi against armed Houthi rebels.

The war has killed an estimated 10,000 people, 2,200 of them children, and pushed the country to the brink of famine.