The attack on the Houthi-rebel controlled area of Dahyan early on Thursday morning overwhelmed local health facilities, said Abdul-Ghani Nayeb, a health department chief in Saada province.
At least 61 people are being treated for their injuries and it is feared the death toll will rise. It is not clear how many of the dead were travelling on the bus or whether pedestrians were caught up in the attack.
Rebel-run Al Masirah TV showed footage of small children covered in blood being carried onto hospital beds. At the scene, a huge column of black smoke towered over the town.
“Scores killed, even more injured, most under the age of 10,” Johannes Bruwer, the head of delegation for the International Committee of the Red Cross (ICRC) in Yemen, said in a tweet.
“Under international humanitarian law, civilians must be protected during conflict.”
The Saudi-led coalition accused the Houthis of using children as human shields, adding that the strike was a “legitimate military operation carried out in accordance with humanitarian law”.
The attack had targeted a Houthi missile launching site which has been used to target the Saudi city Jizan, just over the border. A Houthi strike on the industrial city on Wednesday killed one Yemeni citizen and injured 11 other people.
The UN’s human rights office estimates at least 16,000 people have been killed in Yemen’s three-year-old civil war – many of them by coalition airstrikes – and warns the true figure is likely to be far higher.
The coalition, which has supported Yemen’s exiled government in its fight against the Iran-backed Houthis since 2015, has been frequently accused of not taking adequate precautions to safeguard civilians in its military operations.
Last week, in the rebel-held port city Hodeidah, Yemeni medical officials said coalition airstrikes killed at least 28 people and wounded a further 70, but the Riyadh operations centre denied an attack took place, blaming the deaths instead on the Houthis.
Also on Thursday, several strikes hit the rebel-controlled capital, Sanaa, although it was not immediately clear if there were casualties.
The conflict is in a stalemate that has turned Yemen into the world’s worst humanitarian crisis, sparking the biggest cholera epidemic in modern history and leaving at least eight million people on the brink of starvation and 22 million in need of humanitarian aid.
Britain, the US and other Western countries have been heavily criticised for increasing arms sales to Saudi Arabia and the UAE in the past few years, shipments which campaigners say are destined for use in the complex conflict.
The UN has made tentative progress in restarting stalled peace talks, the first round of which are scheduled in Geneva next month.
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