Three civilians were killed and nine wounded when a mortar shell hit a crowded market in southwestern Yemen, Doctors Without Borders (MSF) said Wednesday.
The shell struck a market in Taiz, a city just inland from the Red Sea port of Mocha and under siege by Yemen's Huthi rebels, the non-profit said on Twitter.
MSF did not say when the raid took place or give details on who was responsible.
Allied with Iran, the northern Huthis are locked in a war against the government of President Abedrabbo Mansour Hadi, who is backed by a powerful military alliance led by Saudi Arabia and the United Arab Emirates.
Nearly 10,000 people have been killed in the Yemen conflict since 2015, when Saudi Arabia and its allies joined the government's fight against the Huthis. More than 2,200 of them were children.
The conflict has pushed the impoverished country to the brink of famine, triggering what the United Nations says is the world's worst single humanitarian crisis.