DUBAI (REUTERS) - The United Nations envoy to Yemen, Jamal Benomar, resigned on Wednesday, according his official Facebook page, signalling the failure of UN efforts to end fierce fighting in the country.

Benomar, a veteran Moroccan diplomat, brokered a 2011 transition plan aimed at quelling political turmoil in Yemen. However, it subsequently unravelled, culminating in an on-going Saudi-led bombing campaign against Iran-allied Houthi rebels.

"A successor shall be named in due course. Until that time and beyond, the United Nations will continue to spare no efforts to re-launch the peace process in order to get the political transition back on track," the statement said.

A UN diplomatic source said Secretary General Ban Ki Moon was considering appointing Mauritanian diplomat Ould Cheikh Ahmed to the post.

A Western diplomat said Ahmed was "in the mix" as a candidate, adding that a final decision had not been made. Several diplomats said it had been known for months that Benomar wanted to leave the Yemen post.

Benomar had irked Saudi Arabia and other Gulf nations for his handling of so far unsuccessful peace talks between the Houthis and the Western and Gulf Arab-backed Yemeni government, Western UN diplomats said on condition of anonymity.

Both the Houthis and Saudi-based Yemeni President Abd-Rabbu Mansour Hadi had also grown impatient with the envoy, Yemeni political sources told Reuters, and UN-sponsored talks repeatedly gave way to armed clashes between the two sides.