Human Rights Watch is calling for an immediate end to all arms sales to Saudi Arabia in the aftermath of the bombing of a schoolbus last month that killed 51 people, including 40 children.



In a report released Sunday, the HRW called the attack an "apparent war crime," saying it only added to the Saudi-led coalition's "already gruesome track record of killing civilians at weddings, funerals, hospitals and schools in Yemen.''



The coalition, which has the support of the United States, has been fighting the Houthi rebels since March 2015. The coalition backs Yemen's internationally recognized government of Abd-Rabbu Mansour Hadi and aims to restore it to power.



The HRW report comes just a day after the coalition said it has accepted the conclusions of its investigative body that there were "mistakes'' made in the attack, including failing to take measures to minimize collateral damage.



The coalition vowed to "take all the legal measures to hold accountable those who were proven to have committed mistakes'' once it officially receives the findings. It also pledged to coordinate with Yemen's government to compensate civilians.



The U.S. State Department on Sunday welcomed the coalition's statement as "an important first step toward full transparency and accountability.''



But, Bill Van Esveld, senior children's rights researcher for HRW, urged the U.S. and other countries to "immediately stop weapons sales to Saudi Arabia and support strengthening the independent U.N. inquiry into violations in Yemen, or risk being complicit in future atrocities.''