Speaking in the Iranian capital of Tehran on Monday, O'Brien described the humanitarian crisis in Yemen as a very bad one, saying that he has talked about the Arabian Peninsula country more than anyone and made serious efforts to resolve the ongoing crisis there, although sometimes he has felt like he is talking to “an empty room”.

Eighty percent of population of the crisis-hit Yemen need humanitarian assistance, the UN official noted.

Currently, the UN is providing emergency relief for 5 million people of the Arab country, he said, adding that UN teams are stationed there.

He further called for expanding regional cooperation between Iran and the UN Office for Coordination of Humanitarian Affairs (OCHA) especially on preparedness for and response to natural disasters in the Middle East.

The remarks came as Yemen’s defenseless people have been under massive attacks by the coalition led by the Saudi regime for nearly 17 months but Riyadh has reached none of its objectives in Yemen so far.

Since March 2015, Saudi Arabia and some of its Arab allies have been launching deadly airstrikes against the Houthi Ansarullah movement in an attempt to restore power to the fugitive former President Abd Rabbuh Mansour Hadi, a close ally of Riyadh.

Nearly 10,000 Yemenis, including 4,000 women and children, have lost their lives in the deadly military campaign.