The United States called for a "thorough" investigation following the deaths of 29 children in northern Yemen in a strike on a bus carried out by the Saudi-led coalition.
State Department spokeswoman Heather Nauert said the US was "concerned" by reports of an attack resulting in civilian deaths.
"We are calling the Saudi led coalition to conduct a thorough and transparent investigation into the incident," she said.
Nauert added the US takes credible accounts of civilian casualties "very seriously." "We call on the parties to take appropriate measures to protect civilians," she said.
A hospital in Saada province supported by the International Committee of the Red Cross "received the bodies of 29 children under the age of 15, and 48 wounded, including 30 children," the organization announced on Twitter.
A spokesman for the Red Cross in Sanaa told AFP the toll was not final as casualties from the attack were taken to several hospitals.
The coalition acknowledged carrying out a "legitimate military action," but spokesman Turki al-Maliki told AFP claims that children were inside the bus were "misleading," adding that the bus carried "Huthi combatants."