Dozens of people, many of them school children, have been killed or wounded in a Saudi-led coalition air strike in rebel-held northern Yemen, medics say.
The bus was travelling through Dahyan market in Saada province at the time.
The health ministry run by the rebel Houthi movement said 43 people were killed. The Red Cross said most of the victims were under the age of 10.
The coalition, which is backing Yemen's government in a war with the Houthis, said its actions were "legitimate".
It insists it never deliberately targets civilians, but human rights groups have accused it of bombing markets, schools, hospitals and residential areas.
What happened in Saada?
Yemeni tribal elders told the Associated Press that the bus was hit as it passed through the Dahyan market and that it was transporting local civilians, including many school children.
The International Committee of the Red Cross (ICRC) said a hospital it supported in Saada had received dozens of casualties on Thursday after the attack.
The head of the humanitarian organisation's delegation in the country, Johannes Bruwer, later tweeted that "scores" had been killed and "even more injured, most under the age of 10".
He said additional supplies were being sent to hospitals to cope with the influx.
Houthi-run Al-Masirah TV reported that 47 people were killed and 77 wounded, and broadcast graphic pictures showing the bodies of several young children, some of them wearing school uniform.