The Saudi attacks on Yemen's infrastructure and civilian targets is "a continued and flagrant violation of human rights", Marziyeh Afkham said on Tuesday.
"According to the international law and regulations, countries should facilitate the activities of relief and rescue organizations affiliated with the UN and their representatives…," she noted.
A guard was injured when the office of the UN Development Program in the southern city of Aden was hit on Sunday, according to UN spokesman Farhan Haq.
UN Secretary-General Ban Ki-moon also deplored the airstrike, calling for a full investigation into the incident.
On March 26, Saudi Arabia and some of its Arab allies began to launch 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.
According to a civil coalition monitoring Saudi Arabia's crimes, 3043 people, including 722 children and 532 women, have been killed during 95 days of Saudi-led military strikes on the Arab country.