TEHRAN, September 13 - The United Nations has warned about the rapidly worsening humanitarian situation in Yemen’s blockaded Hudaydah as fighting between the co un try’s army troops, backed by fighters from the Houthi Ansarullah movement, and militiamen loyal to former president Abd Rabbuh Mansur Hadi resumed in the port city following the collapse of the latest ro un d of UN-brokered peace talks.