The Washington-led alliance puts the toll at just over 1,000 civilians in both Syria and neighbouring Iraq, and says it does all it can to prevent civilian deaths.
Doctors and medics in two hospitals in Hodeida province said 50 people have been killed in the past 24 hours, seven of them pro-government fighters.
Clashes and air strikes have left 84 people dead around Yemen's Red Sea port city of Hodeida since the collapse of UN-brokered peace talks, hospital sources said Sunday.
Saudi Arabia is leading a Western-backed alliance of Arab states trying to restore the internationally recognised government of Yemeni President Abd-Rabbu Mansour Hadi.
The attack on Ghazni, a strategic centre on the main road linking the capital Kabul with southern Afghanistan, has come as a severe blow to President Ashraf Ghani.
A Yemeni health official and the International Committee of the Red Cross said than an air strike had hit the bus carrying children as it drove through a market in northern Saada province.
A Saudi-led coalition launched heavy air strikes on Yemen's main port city of Hodeidah on Friday, in an apparent resumption of military operations on the city after the Iranian-aligned Houthi movement attacked two Saudi oil tankers, residents said.
Unidentified air strikes have killed 12 civilians in a rebel-held pocket of southern Syria as regime ally Russia presses talks for Damascus to retake the area, a monitor said Wednesday.
Air strikes on Tuesday killed seven civilians in a sensitive southwestern province of Syria bordering the Israeli-occupied Golan Heights, a war monitor said.
Rebels controlling several towns in southern Syria were on Friday considering a deal for a regime takeover in exchange for an end to fierce bombing, state media and a monitor said.