A doctor treats children injured by an airstrike in Saada, Yemen on August 9, 2018. (REUTERS)

SANAA, Aug. 9 (Xinhua) -- At least 43 civilians, mostly children, were killed on Thursday when Saudi-led coalition air strikes hit buses in Yemen's northern province of Saada, the head of Saada Health Office Yahya Shayem told Xinhua.

"A total of 43 people, mostly pupils under the age of 10, were killed and 64 were injured when two Saudi-led airstrikes hit passenger buses in Dhahyan popular market," Shayem said, adding that "the victims were mostly pupils who were on their way to attend a summer school in Dhahyan."

Meanwhile, head of delegation for the International Committee of the Red Cross (ICRC) in Yemen, said on a twitter that "scores killed, even more injured, mostly under the age of 10" after the attack targeted a bus that carries children in the Dhahyan market.

The organization stressed that "civilians must be protected during conflict under international humanitarian law."

However, the Saudi-owned Al Arabiya television quoted a statement by the Saudi-led coalition as saying that "Thursday's airstrikes targeted Iranian-allied Houthi rebels who fired a ballistic missile on Wednesday at the Saudi commercial city in border Jazan region."

In response, Houthi spokesman Mohammed Abdulsalam mocked the coalition statement as "absolutely ridiculous."

"They killed pupils driving to school ... this is a war crime," Abdulsalam tweeted.

The Houthi spokesman's comments came at the same time the coalition warplanes hit the Houthi-controlled capital Sanaa 11 times, with no reports of casualties yet. The airstrikes targeted Sabeen Square and two military camps in Sanaa.

The Saada attack was the latest in a series of recent airstrikes against civilians launched by the Saudi-led coalition on Yemen.

Last week, the Saudi-led coalition airstrikes struck the gate of al-Thawra hospital and adjacent fish market in Yemen's Red Sea port city of Hodeidah, killing 52 civilians and wounding 102 others.

The impoverished Arab country has been locked in a civil war since the Houthi rebels overran much of Yemen militarily and seized all northern provinces in 2014, including the capital Sanaa.

Saudi Arabia leads an Arab military coalition that has intervened in the Yemen war since 2015 to support the government of exiled President Abd-Rabbu Mansour Hadi.

More than 10,000 Yemenis, mostly civilians, have been killed in the war, and about 3 million have been displaced.