South Sudan's main opposition group, the Sudan People's Liberation Army In Opposition (SPLA-IO), has apologised following a report that its forces had last month arrested UN staff.

The group is a signatory to a 2018 peace agreement that ended six years of conflict and saw its leader, Riek Machar, appointed as vice-president.

Ceasefire monitors on Tuesday reported that the SPLA-IO forces arrested and detained UN staff and civilians at Farajalla village in Western Bahr El-Ghazal State.

Maj Gen Martin Abucha, a SPLA-IO representative, condemned the incident.

“I would like to apologise on behalf of SPLM-SPLA-IO for the incident that happened where a number of NGO staff were detained, but subsequently released."

"That was unfortunate and we do not condone it in any way. We have taken measures to ensure that it doesn’t repeat itself,” Gen Abucha said.

Ceasefire monitors also reported that the parties to the peace agreement “continue to violate the truce” and blamed them for non-compliance.

South Sudanese various forces are expected to form a unified national army of 83,000 soldiers in accordance with the peace agreement, but they are yet to unify a command and graduate forces.