A group of activists detained in the United Arab Emirates (UAE) are enduring conditions that may amount to torture, a UN expert says.
UN Special Rapporteur Mary Lawlor says the five detainees are being held in solitary confinement for long periods and had their air conditioning switched off in temperatures above 40C.
She called for them to be immediately released after eight years in jail.
The UAE said the allegations were "incorrect and baseless".
Mohamed al-Mansoori, Hassan Mohammed al-Hammad, Hadif Rashed Abdullah al-Owais, Ali Saeed al-Kindi and Salim Hamdoon al-Shahhi are part of UAE94, a group of 94 lawyers, university lecturers and students who were sentenced to 10 years in prison in July 2013 for plotting to overthrow the government.
Their sentences were "excessively severe" and they should have "never been detained in the first place for legitimately exercising the freedoms that all people are entitled to", said Mary Lawlor, the UN's special rapporteur on the situation of human rights defenders.
Ms Lawlor says there are "worrying allegations that they are subjected to long periods in solitary confinement, which could amount to torture".
She also said there were allegations they were being left without air conditioning as temperatures rose above 40C, and that windows were being covered to prevent prisoners from seeing sunlight.
Their access to legal counsel during the trial may have also been severely curtailed, the UN said.
After the 2011 Arab Spring uprising, the UAE launched a crackdown on Islamists it accused of being part of the Islamist group al-Islah, which the authorities say has links to the Muslim Brotherhood that plotted to the overthrow the government.
Political parties and demonstrations are banned in the UAE, which comprises seven sheikhdoms run by ruling families.
Matthew Hedges, a 31-year-old British academic who was jailed for spying in the UAE, has said he endured "psychological torture" during his imprisonment in 2018.
Responding to Ms Lawlor's report, the UAE's Human Rights Director, Saeed Rashid Al Habsi, said the allegations were without foundation.
He said the detainees had never been placed in solitary confinement, nor subjected to any form of torture or inhuman treatment.
"The United Arab Emirates is a signatory to the United Nations Convention against Torture and has served on the United Nations Human Rights Council," he said. "Any complaint or allegation of improper treatment by an inmate or allegation concerning the rule of law is fully investigated."
Update 18 June 2021: Since the story was published, the UAE authorities have responded to the allegations made by the UN Special Rapporteur.