UN Secretary-General Ban Ki-moon condemned an air strike on a school in northern Yemen that killed 10 children and called for an investigation, while the Saudi-led coalition said the attack had targeted a training facility run by the Houthi group.
Aid group Medecins Sans Frontieres said 28 other children were wounded in Saturday's attack on the school in the Saada province. The United Nations Children's Fund said the facility was a religious school in Juma'a Bin Fadil village in the province's Haydan district.
Dozens of air strikes have hit civilian facilities in Yemen since a coalition of Arab states led by Saudi Arabia began military operations in March 2015 to restore President Abd-Rabbu Mansour Hadi to power and roll back gains by the Iran-allied Houthis.
A spokesman for Ban said he condemned the attack and urged parties "to prevent further violations of international humanitarian law and human rights and do everything in their power to protect civilians and civilian infrastructure."
A spokesman for the Saudi-led military coalition did not respond to requests by Reuters for a comment on the reports. But Saudi media quoted General Ahmed al-Assiri as telling media that the coalition had targeted a centre used by the Houthi militias as a training camp.
The coalition accuses the Houthis of recruiting children to fight in the conflict that has claimed more than 6,400 people, half of them civilians, according to UN figures and displaced 2.5mn people.
The Saudi-led coalition intervened in Yemen after the Houthis advanced on Aden in 2015, forcing Hadi and his government to flee the country.
The coalition and Hadi's forces have made some gains, driving the Houthis out of a few cities but have so far failed to achieve a victory against the group.