The statement described the attack as "one of the deadliest attacks on children since the conflict in Yemen escalated in March 2015".
A Saudi-led military coalition intervened in Yemen on March 26, 2015 to try to restore the government of President Abedrabbo Mansour Hadi.
The UN said Friday that surging violence across Yemen had pushed some 85,000 people from their homes in the past 10 weeks, with hundreds continuing to flee each day.
Yemeni separatists have surrounded the presidential palace in the government's interim capital Aden, a military source said Tuesday.
Fourteen soldiers were killed on Tuesday in a suicide attack by suspected Islamist extremists in southern Yemen, a senior military official said.
The Saudi-led military coalition which supports the government called for dialogue and for it to hear the demands of the separatists in the southern port city.
Saudi Arabia said Wednesday it had intercepted a fresh missile attack by Yemeni rebels on the south of the kingdom and renewed its accusations that arch-foe Iran had armed them.
Yemen's rebels have threatened to block traffic across the Red Sea unless a blockade by a regional military alliance is lifted, prompting fresh accusations Tuesday of "terrorism" by their rivals.
Saudi-led air strikes on a prison camp run by rebels in Yemen killed 12 people and wounded 80 on Wednesday, the rebels' Al-Masirah TV reported.