Saudi Arabia and the United Arab Emirates (UAE) have admitted that the bombing of a school bus in Yemen last month - which killed 51 people, including 40 children - was "unjustified".
A probe by the coalition fighting Yemen's Houthi concluded on Saturday that "mistakes" had been made in the August 9 air raid in Saada province.
At the day of the attack, coalition spokesperson Colonel Turki al-Malki had defended the air raid, saying his forces hit a "legitimate military target", which included "operators and planners".
But in a rare concession, the military alliance's investigative body, the Joint Incident Assessment Team (JIAT), said that those behind it should be held accountable.
"The Joint Team … is of the opinion that the coalition forces should initiate legal action to try and penalise those responsible for the mistakes, which caused collateral damage in the area," Mansour Ahmed al-Mansour, a legal adviser to JIAT, told reporters in the Saudi capital, Riyadh.
The probe came after the air attack sparked widespread international condemnation and calls for an independent investigation from United Nations Secretary-General Antonio Guterres.
Following the attack, individual members of the Congress in the United States also called on their country's army to clarify its role in the war and investigate whether support for the air raids could render US military personnel "liable under the war crimes act".
The US has been the biggest supplier of military equipment to Riyadh, with more than $90bn of sales recorded between 2010 and 2015.