An explosion near two schools in the rebel-held Yemeni capital killed 14 children and wounded 16, the UN said Tuesday, but the cause of the weekend blast remains unclear.
Most of the child casualties in the city's Saewan district were girls under the age of nine, according to statements by both the UN children's fund (UNICEF) and the UN special envoy for Yemen.
Yemen's Houthi rebels have accused a Saudi-led military coalition backing the government of carrying out an air strike.
The coalition denied conducting any air raids on the capital on Sunday.
"A blast in Sanaa this week killed 14 children and critically injured 16. This is what UNICEF was able to verify, with the actual number of children killed and injured likely to increase," said UNICEF's Middle East and North Africa director, Geert Cappelaere.
"It was almost lunchtime and students were in class. The blast shattered the windows and unleashed a burst of shrapnel and broken glass into the classrooms."
The United Nations and international aid groups have called for an investigation into the Sunday explosion but have not apportioned blame.
The World Health Organization estimates nearly 10,000 Yemenis have been killed since 2015, when Saudi Arabia and its allies intervened to prevent the defeat of the government in the face of a rebel offensive.
Human rights groups say the real death toll is several times higher.
The conflict has pushed millions of Yemenis to the brink of mass starvation, in what the UN has called the world's worst humanitarian crisis.
Both sides stand accused of actions that could amount to war crimes. The coalition has been blacklisted by the UN for the killing of children.
Saudi Arabia and its allies accuse the Houthis of using civilians as human shields in densely populated areas.