Former UN Secretary-General Kofi Annan has quit his role as the U.N.-Arab League joint special envoy to Syria apparently out of frustration over Syria’s aggravating civil war.

UN Secretary-General Ban Ki-moon said at the UN headquarters in New York on Thursday that he was announcing with deep regret Annan's resignation. Ban noted that Annan had expressed his wish to resign earlier on Tuesday.

Ban said he is consulting with Secretary-General of the League of Arab States Nabil El Araby on who to appoint as Annan’s successor.

Annan apparently decided to call it quits in protest of Russia continuously voting down resolutions seeking to bring an end to the violence in Syria.