Syria's opposition has postponed its "formal participation" in peace talks in protest over escalating violence, but will remain in Geneva and may continue informal discussions with mediators, the UN envoy said Monday. 

"I heard today from the HNC (opposition High Negotiations Committee) their intention to postpone their formal participation in the (UN) to the negotiations to express their own displeasure due to the deterioration of the humanitarian situation and (of) the cessation of hostilities," UN mediator Staffan de Mistura told journalists. 

He added that HNC delegates may continue to meet UN staff at their hotel "to pursue technical discussions", including on political transition in Syria.