Fifty-six children were also among the 79 people wounded in the Thursday strike on Saada province, a rebel stronghold that borders Saudi Arabia, the International Committee of the Red Cross said in a new toll.

The child deaths have been an embarrassment for Western governments which supply the coalition with warplanes and other weapons and have sought to prevent the conduct of the war being scrutinised too closely.

The coalition has promised an internal inquiry but analysts and aid groups have voiced doubt it is ready to provide the transparency and accountability demanded by the wider international community.

The new casualty toll came after a mass funeral was held for many of the dead children on Monday at which thousands vented anger against Riyadh and Washington.

Mourners raised pictures of the children and shouted slogans against Saudi Arabia and its ally and key arms supplier, the United States.

The Saudi-led coalition intervened in Yemen in March 2015 as Huthi rebel fighters closed in on the last bastion of President Abedrabbo Mansour Hadi's government.

The conflict has killed nearly 10,000 people since then -- the vast majority of them civilians -- and caused what the United Nations has described as the world's worst humanitarian crisis.

The UN Security Council called on Friday for a "credible" investigation into the deadly strike.

But it stopped short of demanding an independent inquiry as urged by UN chief Antonio Guterres after past probes failed to lead to any significant reduction in the high civilian death toll from the coalition's more than three-year bombing campaign.

- Western powers back ally -

The coalition has been repeatedly blamed for bombing civilians, including a strike on a wedding hall in the Red Sea coastal town of Mokha in September 2015, in which 131 people died. It denied any responsibility for those deaths.

In October 2016, a coalition air strike killed 140 people at a funeral in the rebel-held capital Sanaa.

Coalition commanders have admitted a small number of mistakes, but there has been no public disciplinary action or changes to the rules of engagement.

Commander have accused the rebels of using civilians as human shields.

The coalition initially called the strike on the bus a "legitimate military action" in response to a rebel missile attack on the Saudi city of Jizan on Wednesday.

But as photographs of dazed and bloodied children flooding into hospitals were beamed around the world, it was forced to concede to an investigation.

Western government have condemned the civilian deaths, but they remain political and military backers of Saudi Arabia, which is a regional ally and spends billions of dollars on arms from the United States, Britain and France.

During US-led air campaigns in Afghanistan, Iraq and Syria since 2001, Western forces occasionally admitted "collateral damage" when civilians were killed unintentionally.

But they too resisted independent investigations into the circumstances of major errors.

Key Saudi coalition ally, the United Arab Emirates, said Monday that the child deaths were a manifestation of the "ugly" side of war for which both sides were to blame.

"Unfortunately, this is really part of any confrontation," the UAE's minister of state for foreign affairs, Anwar Gargash, said, adding that those calling for independent investigations should instead urge tighter rules of engagement.