The United Nations torture watchdog urged Syria, Yemen and Jordan on Friday to investigate what it called numerous and credible allegations that their police and prison authorities routinely tortured detainees.
Its 10 independent experts also voiced concern at "honour" crimes by family members in Syria and Jordan which go unpunished and violence against women and children in Yemen.
Their conclusions on a total of eight countries were issued at the end of a three-week meeting.
In Yemen, it voiced alarm at killings, forced disappearances, torture, arbitrary arrests and indefinite detentions without charge or trial carried out in the context of the fight against terrorism.
There was a "climate of impunity for perpetrators of acts of torture in Yemen," the UN Committee against Torture said.
"No exceptional circumstances whatsoever can be invoked as a justification for torture and...anti-terrorism measures must be implemented with full respect for international human rights law," it added.
Yemen's government, struggling to stabilise a fractious country in which central authority is often weak, faces international pressure to quell domestic conflicts in order to fight a resurgent al Qaeda.
The UN torture watchdog also voiced concern at reports it haD received that Syria has set up secret detention facilities under the command of intelligence services, where inmates are held incommunicado and subject to cruel treatment.
It cited "numerous reports of torture, ill-treatment, death in custody and incommunicado detention of people belonging to the Kurdish minority, in large part stateless, in particular political activists of Kurdish origin."
"Moreover, the committee notes with concern reports of a growing trend of deaths of Kurdish conscripts who have died whilst carrying out their mandatory military service and whose bodies were returned to the families with evidence of severe injuries," it said of Syria.
The UN experts urged Syrian authorities to clarify the case of Muhannad al-Hassani, president of the Syrian Organisation for Human Rights, who was arrested last July on charges of "weakening national sentiment."
A lawyer who has defended leading opposition figures, he won an international human rights award last week.