UN human rights experts have urged the UAE to release five Libyans who they say are being detained arbitrarily.
The men, three of whom have US or Canadian dual nationality, were arrested in August 2014.
Two went on trial in late 2015, while three were only charged last month with funding, supporting and co-operating with terrorist organisations.
The UN experts said there was credible information they had been tortured and forced to sign confessions.
Most were also suffering from serious health conditions as a result of their mistreatment and a lack of access to adequate medical care, the experts added.
UAE response 'unpersuasive'
The experts identified the detainees as Salim Alaradi, a Libyan-Canadian citizen; Kamal Ahmed al-Darrat and Mohamed Kamal al-Darrat, father and son, both Libyan-American citizens; and Adel Rajab Beleid Nasef and Moad Mohamed al-Hashmi, both Libyan citizens.
Following their arrest by State Security officials, the men were allegedly held incommunicado in secret detention locations and in solitary confinement for prolonged periods of time.
Mr Alaradi and Kamal and Mohamed al-Darrat were charged with funding, supporting and co-operating with alleged terrorist organisations on 18 January. Their trial was scheduled to open on Monday.
However, the UN experts expressed concern that the three men had been charged under a law that had not yet entered into force at the time of their arrest.
Earlier this month, Human Rights Watch said they had denied the charges and alleged they had been tortured into confessing links to the Muslim Brotherhood, which was designated a terrorist group by the UAE in November 2014.
Mr Nasef and Mr al-Hashmi have been charged in a separate case and their trial opened in late 2015.
The UAE government had no immediate comment on the experts' appeal on Monday.
The experts said they had been in contact with authorities previously and found their reply "unpersuasive".