Kofi Annan is quitting as UN-Arab League peace envoy for Syria, UN leader Ban Ki-moon has announced, as the 17-month-old conflict spiralled further out of control.

Ban announced "with deep regret" the resignation of Annan, who was named to the post on February 23.

"I wish to express my deepest gratitude to Mr Annan for the determined and courageous efforts he has made as the Joint Special Envoy for Syria," he said in his statement. 

Annan told Ban and Nabil El Araby, the general-secretary of the Arab League, of his intention not to renew his mandate when it expires on August 31, 2012.

Ban said in the statement that he and El Araby were in discussions on appointing a successor to Annan.

To read the full statement by the UN secretary-general click here.

Annan cited "finger-pointing and name-calling" in the 15-nation Security Council as one of the reasons for his decision to step down, at a press conference in Geneva and in an article published in the UK daily Financial Times on Thursday.

Responding to the news Amnesty International's Head of Office and Representative at the United Nations Jose Luis Diaz said:

"The Kofi Annan resignation again points up the failure of the UN Security Council [UNSC] to act in a united and decisive way to help put a stop to the violence in Syria.

"Following repeated blocking by permanent members Russia and China, it took nearly a year from the start of the crisis for the UNSC to adopt watered down measures on Syria. In the meantime the killing and crimes under international law continued, and goes on to this day. As Annan said in Geneva today while expressing his frustration, when the Syrian people desperately need action, there continues to be finger-pointing and name-calling in the Security Council.

"UNSC members have seemingly been guided more by political and strategic considerations than by the need to protect the human rights of the Syrian people."

Read our news story for more detail and context: Annan quits as Syria peace envoy


Annan leaves after a news conference at the United Nations in Geneva on Thursday [Photo: Reuters]