A Saudi-led coalition air strike hit a bus carrying children in rebel-held northern Yemen on Thursday, killing and wounding dozens.
The Saudi-led coalition later said the airstrikes were aimed at missile launchers used to attack the southern Saudi city of Jiza, claiming its strike constituted a "legitimate action".
The International Committee of the Red Cross said it was sending supplies to ICRC-supported hospitals to support an influx of casualties.
A hospital in Saada province supported by the International Committee of the Red Cross "received the bodies of 29 children under the age of 15 and 48 wounded, including 30 children", the organization announced on Twitter. Despite killing dozens of schoolchildren, the spokesman called Thursday's attack on the school bus a "legitimate military action" and said it is "in accordance with worldwide humanitarian law and customs".
In the Yemeni capital, rebel-run Al Masirah TV gave a different number, saying the attack killed 39 people and wounded 51, mainly children.
The attack was also denounced by the United Nations children agency, UNICEF.
"The attack carried out today by the coalition in Saada was against those people responsible for the ballistic missile attack last night ... the allegation [that civilians were targeted] is coming by the Houthis, and it's still an allegation", Col Al Maliki said. Turki Al-Maliki, the official spokesman of the Coalition as stating on Thursday.
In March 2015 Saudi Arabia and other Arab states intervened on against the Houthis, and are continuing to do so.More news: Everton linked with Welbeck move with Arsenal ready to sell
Speaking by phone to the US-based news outlet, spokesman for the Saudi-led coalition supporting Yemen's government, Col Turki Al Maliki, insisted Thursday's attack carried out in Saada is a "legitimate military action" and is "in accordance with worldwide humanitarian law and customs".
The Western-backed alliance fighting the Iranian-aligned Houthi group in Yemen accused the Houthis of using children as human shields.
Turki al-Malki said the attack was "a legitimate military action, conducted in conformity with worldwide humanitarian law".
Footage from the Houthi media office showed a boy wearing a blue backpack with a UNICEF logo being carried into a hospital emergency room with blood pouring down his face and over his traditional Yemeni thawb, an ankle-length garment.
The coalition denied responsibility for those attacks.
Global rights groups repeated calls for an end to the war and strongly condemned the bus attack and other civilian massacres.
"It's hard to believe we live in a world where children should live in fear of such attacks, yet here we are", she added. We urge all parties to agree to an immediate cessation of hostilities, return to the negotiation table to commit to a ceasefire and cooperate with the U.N. Special Envoy Martin Griffiths.
UN-brokered negotiations on Yemen broke down in 2016 amid demands for a rebel withdrawal from key cities and power-sharing with the Saudi-backed government.