At least 50 people, including several children, were killed and scores injured in Thursday’s air raid on a bus in Saada.

There is grief and anger in Yemen‘s war-ravaged province of Saada a day after the Saudi-UAE military alliance, backed by the US, bombed a school bus carrying children heading to a Quran class.

Al Masirah, a pro-Houthi TV network, said at least 51 people were killed in the attack which struck the bus as it was approaching a crowded market in Dahyan city.

Johannes Bruwer, the head of a delegation for the International Committee of the Red Crescent (ICRC) in Yemen, said in a Twitter post that 40 children were killed, and more than 79 people were wounded, 56 of them under the age of 15.

Final information issued by Sa’ada authorities. Out of a total number of 130 victims, 51 dead, including 40 children, and 79 injured out of which 56 are children. The numbers speak for themselves. — Johannes Bruwer (@JohannesBruwer1) August 10, 2018

Hussain al-Bukhaiti, a pro-Houthi activist, told Al Jazeera that the death toll was expected to rise in the coming days.

“Most of the hospitals and clinics in Saada have either been completely destroyed or are badly damaged, and most lack basic medicines. So, how will they treat the wounded?” he said.

According to the ICRC, one of the few humanitarian institutions helping civilians in the country, all of the children who were admitted to its hospital were under the age of 15.

The Saudi-UAE alliance later issued a statement to the Saudi-owned Al-Arabiya network confirmed it launched attacks on Saada, and accused Houthi fighters of using the children as human shields.

“[The air strikes] conformed to international and humanitarian laws,” a statement quoting coalition spokesman Colonel Turki al-Malki said.

‘Where are my brothers?’

In unverified videos uploaded to social media, bereaved parents could be seen pleading with hospital staff for updates, as dead bodies literally began piling up, on top of each other.

In one video, a father could be seen struggling to contain his grief after he found his dead son under a heap of corpses in the boot of a Nissan pick-up truck.

In a second video, one of the children who survived the attack refused to receive medical attention until doctors updated him on the fate of his two younger brothers.

“I have two brothers, Hassan and Yehia, who are smaller than me,” the boy said. “Where are my brothers? … I don’t want help until I see my brothers.”

It was not clear if the boy’s brothers had survived.

Pictures from the scene of the attack showed homes and businesses destroyed, with trails of blood on the roads and UNICEF backpacks splattered with blood.

“I am watching with horror the images and videos coming from Saada in #Yemen and I have no words. How was this a military target? Why are children being killed?” tweeted Meritxell Relano, UNICEF’s resident representative in Yemen.

‘Silence legitimises Saudi aggression’

Yemen’s rebel-run Ministry of Defense issued a statement early on Friday, saying: “The silence of the international community legitimised [the Saudi-UAE alliance’s] continuing aggression and brutality.

“By staying silent about these crimes, they are accomplices in the deaths of women and children.”

The ministry’s comments came shortly after the US Department of State called on Saudi Arabia “to conduct a thorough and transparent investigation into the incident”.

Previous investigations by the Saudi-UAE alliance have seen them absolve themselves of any real responsibility and instead pinned the blame on the Houthis.

Meanwhile, the UN, which has repeatedly criticised the alliance’s bombing campaign and last year placed it on a blacklist of child rights violators, called for an independent investigation.

Houthi leader Mohammed Ali al-Houthi said on Twitter that the rebels would “cooperate” if needed.

Muhsin Siddiquey, Oxfam’s country director for Yemen, called on UN Security Council members to exert more pressure on the Saudi-UAE alliance, and “demand an immediate ceasefire” and the “resumption of peace talks.”

“Hitting a bus carrying school children near a crowded market is simply unacceptable,” Siddiquey told Al Jazeera.

“Countries that have power in the UN Security Council should hold the conflicting parties accountable under international humanitarian law.

“The US, UK, France and other powers have a moral obligation to pressure the conflicting parties. They need to do more.”

Al Jazeera’s Mohammed Adow, reporting from neighbouring Djibouti, said while Yemenis were still grieving, the UN’s announcement was going to “instil hope in some Yemenis who thought the world had totally forgotten about them”.

“This is one of the worst attacks to have hit north Yemen [since the war started]. It’s caused an all too familiar devastation that we’ve become all too accustomed to seeing”.

With logistical support from the US, Saudi Arabia and the UAE have carried out attacks in Yemen since March 2015. The war effort is ostensibly an attempt to reinstate the internationally recognised government of President Abu-Rabbu Mansour Hadi .

In 2014, Hadi and his forces were overrun by Houthi rebels who took over much of the country, including Sanaa.

Earlier this month, dozens of people – including women and children – were killed in Yemen’s Red Sea port city of Hodeidah in mortar attacks believed to be carried out by the Saudi-UAE alliance.

According to the UN, at least 10,000 people have been killed in the three-year war – a death toll that has not been updated in years and is certain to be far higher.

In June, Saudi and UAE forces carried out 258 air raids on Yemen, nearly one-third of which targeted non-military sites.

The Yemen Data Project listed 24 air raids on residential areas, three on water and electricity sites, three hitting healthcare facilities, and one targeting an IDP camp.