The UN Committee against Torture has asked Cameroon to stop its troops from committing "atrocities" in its fight against Boko Haram jihadists, according to report seen by AFP on Thursday.
The body also expressed concern over sweeping arrests in the Francophone west African country's English-speaking regions, demanding an investigation into the deaths of at least 17 people killed in October 1 clashes between the security forces and protestors seeking a separate state.
It said more than 500 people were arrested, some of them from the hospital in the wake of the unrest, and criticised Yaounde for not responding to several demands seeking information on those still being held.
Boko Haram, the Islamist militants whose insurgency has left at least 20,000 people dead and more than 2.6 million others homeless since 2009, has spread its attacks from Nigeria to neighbouring countries, including Cameroon.
The report denounced "serious crimes and atrocities committed by the Boko Haram terrorist group in the extreme north since 2014," but underscored its "great concern" over reports of abuses and torture by Cameroonian security forces.
The committee said it had received information that many people in the Extreme North region had been "detained in secret on suspicion of backing Boko Haram... in at least 20 unofficial detention centres."
The report said the state was protecting the security forces from being probed for "extra-judicial executions, forced disappearances and arbitrary detentions."
Cameroon is among the 162 countries that are signatories to the convention against torture.
"With the Committee against Torture now also demanding an end to the use of torture in Cameroon, it is becoming impossible for the world to ignore the widespread practice of torture in the country," said Ilaria Allegrozzi, Amnesty International's Lake Chad researcher, said on Thursday.
The committee met in Geneva early last month and reviewed the situation in Cameroon. The 10 independent experts held discussions with the Cameroonian delegation before publishing the latest report.