AlQa'dah 21, 1435, Sep 16, 2014, SPA -- The U.N. Human Rights Office Tuesday called on Yemeni officials to conduct an "independent, prompt, and effective investigation" into killings earlier this month of nine protestors in Sana'a. "As Yemen faces various internal challenges, it is more crucial than ever that violations of international human rights law are not swept under the carpet," Rupert Colville, spokesman for the U.N. High Commissioner for Human Rights, told reporters in Geneva. Colville said that to date "no official investigation has been initiated into the alleged excessive use of force." According to the U.N. Human Rights Office (OHCHR), the protestors on September 7 and 9 were armed only with sticks, stones, and umbrellas, when security forces opened fire with live ammunition and without warning. An additional 67 people were reportedly injured, OHCHR said, including 33 by live ammunition and others as a result of the use of tear gas. Colville said that a prompt, impartial investigation would "send a strong signal of deterrence to perpetrators and ensure that victims' right to justice and remedy is upheld."