US-made bomb 'discovered at Yemen school bus bomb site'
Local Yemeni journalists shared photos on Twitter of fragments of a Raytheon Mark 82 general-purpose free-fall bomb purported to have been recovered from the scene.
Freelance journalist Ahmed Algohbary also published videos of himself at the scene with the pieces of the US-made bomb.
The US is well-known to be one of the largest arms providers to Saudi Arabia, selling the kingdom billions of dollars worth of warplanes, weapons and ammunition, as well as supplying replacement munitions, intelligence and refuelling support for coalition aircraft.
Forty children were among 51 people killed in the Saudi-led coalition airstrike on a school bus in Saada, rebel-held northern Yemen, the Red Cross said in a new toll Tuesday.
Fifty-six children were also among the 79 people wounded in the Thursday strike on the northern province, a rebel stronghold that borders Saudi Arabia, the International Committee of the Red Cross said.
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 Houthi rebel fighters closed in on the last bastion of President Abedrabbo Mansour Hadi's government.
The conflict has killed more than 10,000 people since then, the vast majority of them civilians, and caused the world's worst humanitarian crisis, according to the United Nations.
The UN Security Council called on Friday for a "credible" investigation into the deadly strike.
But it stopped short of demanding an independent investigation, and experts and aid groups voiced doubts that a promised coalition probe would provide transparency or accountability.
Washington also called for a "thorough" investigation into the attack, but received backlash for its ongoing support for the Saudi coalition, which is known to target civilians by bombing weddings, funerals and boats carrying refugees.
One such attack consisted of a strike on a wedding hall in the Red Sea coastal town of Mokha in September 2015, in which 131 people died, however the coalition denied responsibility.
In October 2016, a coalition airstrike killed 140 people at a funeral in the rebel-held capital Sanaa.
The coalition has admitted a small number of mistakes, but accuses the rebels of using civilians as human shields.
The high civilian death toll has been an embarrassment for Washington and other Western governments such as the UK and France, which all have lucrative contracts with the kingdom for supplying warplanes and other weapons.
Agencies contributed to this report