Dozens of children, many believed to be under the age of 10 and on their way to summer camps, have been killed after a Saudi-led coalition airstrike hit a school bus in northern Yemen on Thursday.
The bus was struck as it was driving through a market in the rebel-held province of Saada, according to the Houthi-run Al-Masirah TV.
At least 43 people were killed and 63 injured in the strike, according to the Houthi-held health ministry.
The International Committee for the Red Cross (ICRC) said that a hospital it supports in Saada had received 29 dead bodies of "mainly children" under 15 years of age, and 40 injured, including 30 children.
"(The hospital) is very busy. They've been receiving wounded and dead since the morning and it is non-stop ," ICRC head of communications and spokesperson Mirella Hodeib told CNN.
Houthi media broadcast graphic footage appearing to show the dead bodies of children. Another video showed a young boy carrying a UNICEF backpack being escorted to a hospital, his face bloodied as medical staff tried to treat his injuries.
Witnesses that CNN spoke to said the attack could be heard from neighboring districts.
The Saudi-led coalition called the airstrike a "legitimate military operation," and a retaliation to a Houthi ballistic missile that targeted the kingdom's Jizan province on Wednesday night, according to Saudi Arabia's official news agency.
"The targeting that happened today in Saada province was legal military action to target elements that planned and executed the targeting of civilians in the city of Jizan last night, killing and wounding civilians," the Saudi Press Agency cited official coalition spokesperson Turki al-Maliki as saying.
One person was killed in that attack, Saudi state media reported.
Maliki said those responsible for firing ballistic missiles and targeting civilians would "get what they deserve."
The United Nations has repeatedly criticized the actions of the coalition.
"Putting children in harm's way is horrific and deplorable and making them pay such a price is unacceptable," said Hodeib.
Responding to the airstrike on Thursday, UNICEF Regional Director in the Middle East and North Africa Geert Cappelaere said, "does the world really need more innocent children's lives to stop the cruel war on children in Yemen?"