TORONTO (AP) — A regional group assessing South Sudan's peace agreement says members of the National Security Service forced several of its monitors to strip and face "inhuman" treatment.

The report by the Ceasefire and Transitional Security Arrangements Monitoring and Verification Mechanism, seen by The Associated Press, says the four East African monitors were blindfolded, kicked and robbed Tuesday. It said the three men were stripped to their underwear and the woman was stripped naked. They were released hours later.

The harassment occurred in Luri, just west of the capital, Juba. The team was investigating alleged recruitment and training of forces, a violation of the peace deal.

Observers call it the worst attack on the monitoring group since 2016, when a member was killed.

South Sudan's government was not immediately available for comment.