"It has already been finalised. We [have] just signed it [in Bangui]", Chergui said.
He also stated that Russia should be commended for the role it played in the talks.
"We want to thank the Russian Federation for their participation in this process", the commissioner added.
On Tuesday, Central African President Faustin-Archange Touadera and 14 armed groups initiated the peace agreement at talks in Khartoum.
The landlocked CAR has been suffering from a drawn-out conflict since a coup in 2013. Much of the fighting in recent years has been between the Muslim-majority Seleka and Christian Anti-Balaka militias.
It became known on 2 February that the conflicting sides had agreed to establish a mixed border security mechanism between the CAR government, UN troops and representatives of the armed groups.