Yemenis take part in a rally to show support for the Yemeni parliament in Sanaa on Aug. 13. (Yahya Arhab/European Pressphoto Agency)

Ten children died and 28 were injured in what Yemeni locals and officials described as an airstrike on a school in northern Yemen by a U.S.-backed Saudi-led coalition. The aid group Doctors Without Borders confirmed receiving casualties at its medical facility in the area.

The children, according to local reports, were taking exams inside their classrooms in Haydan, an enclave of the city of Saada. Gruesome images of what appeared to be the bodies of the children have emerged on social-media sites.

In a statement released late Saturday night, Maj. Gen. Ahmed al-Asiri, a spokesman for the Saudi military coalition, said the air strike hit a Shiite Houthi rebel training camp and that children were present there as recruits. The claims could not be independently verified.

But Saturday’s attack was the latest airstrike to hit Yemen since U.N.-backed peace talks collapsed a week ago between the Western- and Saudi-backed government of Yemen and Shiite Houthi rebels, who have seized the capital, Sanaa, and other regions. Dozens, mostly civilians, have been killed across the country by the coalition, which dramatically stepped up its air assault Tuesday after five months of relative calm.

In a Twitter feed on Saturday, Doctors Without Borders wrote that the “final number of injured from Haydan school is 28 & 10 deaths. All between 8-15 years old #Saada #Yemen

The conflict began early last year, when President Abed Rabbo Mansour Hadi resigned and fled to the southern city of Aden after Houthi rebels seized and consolidated their hold on Sanaa. Saudi Arabia’s Sunni Muslim monarchy was wary of the Shiite Houthis and their links to Iran, Riyadh’s main rival in the region. So the Saudis and their allies intervened to restore Hadi to power.

The Houthis are also aligned with former President Ali Abdullah Saleh, who remains a powerful presence in the country, and maintain military and political muscle.

The conflict has claimed more than 6,500 lives, about half of them civilians, and has plunged Yemen, already the Middle East’s poorest nation, into a humanitarian crisis and to the brink of famine. Tens of thousands of children, in particular, have felt the brunt of the conflict in myriad ways, including chronic malnutrition and recruitment as soldiers.

Human rights groups have accused the Saudi-led coalition of indiscriminately bombing civilians and systematically committing human rights violations, which Riyadh has denied. Activists and some lawmakers have urged the United States and other Western powers to stop supplying billions of dollars of fighter jets, bombs and other weaponry to Saudi Arabia.

In June, the United Nations placed the Saudi coalition on a blacklist of states and armed groups that kill and maim children in war. About 60 percent of the children killed in Yemen were the victims of airstrikes, according to the United Nations. But the kingdom was swiftly removed from the list after protesting, prompting Secretary General Ban Ki-moon to publicly tell journalists that he had faced “undue pressure” from the Saudis.

Last week, the Pentagon said it planned to sell $1.5 billion more in weapons and military advisory support to Saudi Arabia.

Raghavan reported from Cairo. Sheikha Aldosary in Riyadh, Saudi Arabia, contributed to this report.