"The [Saudi-led coalition] will take all necessary measures against the terrorist, criminal acts of the terrorist Iranian-Houthi militia, such as recruiting child soldiers, throwing them in battlefields and using them as tools and covers to their terrorist acts", Saudi military spokesman Turki AlMalki said in a statement.
That was the toll at just one hospital.
It was unclear how numerous dead in total were children and how many air strikes were carried out in the area, in northern Yemen, near the border with Saudi Arabia.
He stressed that the Houthi leaders and terrorist elements responsible for firing ballistic missiles and targeting civilians will be targeted as part of the coalition efforts to prevent terrorist elements from harming regional and global security.
"We are unable to verify the details at this moment", Save the Children wrote on August 9.
It insists it never deliberately targets civilians, but human rights groups have accused it of bombing markets, schools, hospitals and residential areas.
"Scores killed, even more injured, most under the age of 10", Johannes Bruwer, head of delegation for the ICRC in Yemen, said in a Twitter post.
The World Health Organisation (WHO) representative in Yemen, Nevio Zagaria, said it has deployed emergency supplies.
The ICRC stressed that "under global humanitarian law, civilians must be protected during conflict", while the secretary-general of the Norwegian Refugee Council Jan Egeland called it a "grotesque, shameful" attack that showed "blatant disregard for rules of war".
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The Saudi-led military campaign was launched in support of Yemen's former Riyadh-friendly government and against its popular Houthi movement.
Investigations by the United Nations and the U.S. have found evidence that the missiles fired by the Houthis were supplied by Tehran.
USA bombs. US targeting.
"We are trying to get rid of the arms manifestations in the province, and to carry on the efforts exerted by the UAE to counter the terrorism groups in Yemen", Col Mohammed Salem Al Buhar, commander of the elite forces in Shabwa, told The National. It was not immediately clear if there were any casualties in those strikes.
The attack on Jazan was the second ballistic missile fired at Saudi Arabia by the Iran-backed rebels this week.
He said the leaders and militants responsible for launching ballistic missiles and targeting civilians would be held accountable as part of the coalition's efforts to prevent terrorist elements from compromising regional and global security.
The US, the United Kingdom and other Western powers have been providing arms and intelligence to the alliance in the course of the war, which has unleashed the world's worst humanitarian crisis in Yemen, according to the UN.