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 rebels 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.
Al Jazeera's Alan Fisher, reporting from neighbouring Djibouti, said the statement marked a "remarkable about-turn" after the coalition's initial assertions that this was a legitimate military operation.
"But if you look at the actual wording ... they are not saying that there was a problem with killing children.
"What they are saying is that this attack shouldn't have taken place when it did because they were targeting Houthi leaders, and they say … their intelligence pointed in that direction but those Houthi leaders at that stage did not present a threat to Saudi-led coalition forces and therefore that operation shouldn't have happened," added Fisher.
"They say that intelligence was passed to the pilot who fired the fatal missile but it never got there in time."
The probe came after the air attack sparked widespread international condemnation and calls for an independent investigation from United Nations Secretary-General Antonio Guterres.
Geert Cappelaere, UNICEF's regional director in the Middle East and North Africa, tweeted at the time: "NO EXCUSES ANYMORE!!"
"Does the world really need more innocent children's lives to stop the cruel war on children in Yemen?" he said.
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.
Speaking to Al Jazeera from Yemen's capital, Sanaa on Saturday, Hussain al-Bukhaiti, a pro-Houthi activist, said the coalition's statement was "not an apology".
"It is actually adding insult to injury," he said. "Since the beginning of this war, they have committed many crimes and they only regret or release such a statement only if that crime has been covered widely on the media."
Sama'a al-Hamdani, a visiting fellow at Georgetown University, said "the Saudis had to agree to hold themselves accountable to international standards of law" due to major outside pressure.
"You could make two things from their statement," she told Al Jazeera from Washington, DC. "One, they could potentially change their ways, which is the first step to issuing reparations to the families of those killed. It is also a way to hold them accountable for their actions."
The Saudi-UAE admission on Saturday came a week after Human Rights Watch accused the pair of reaching "dubious conclusions" in its post-air attack analysis and failing to properly investigate alleged war crimes.
In a damning 90-page report, the rights group slammed JIAT for "absolving coalition members of legal responsibility in the vast majority of attacks".
Saudi Arabia, along with the United Arab Emirates, has been bombing Yemen since March 2015 after the Houthis swept across the country, including Sanaa. The coalition's stated aim is to restore the government of President Abd-Rabbu Mansour Hadi to power.
Out of the 16,000-plus raids they have launched since the start of the conflict, only a handful have been investigated, despite nearly a third of all bombs hitting civilian targets.
Last year, the UN blacklisted the Saudi-UAE alliance for causing the majority of reported child deaths and injuries in Yemen.
The global body has described the situation in Yemen as the world's worst humanitarian crisis.
It has also said that least 10,000 people have been killed since the start of the conflict. However, analysts say the death toll is likely to be higher.