Several children were among those killed in a strike on rebel-held Yemeni port Hodeida on Monday, the UN said, calling it "one of the deadliest attacks" on minors in the country for years.
"The United Nations has verified the killing of several children in an attack... in the coastal city of Hodeida in western Yemen," children's agency Unicef said in a statement on Monday.
"Many children are reported missing as the injured and killed are still being pulled out from the rubble."
The statement described the attack as "one of the deadliest attacks on children since the conflict in Yemen escalated in March 2015".
A security source told AFP on Monday that an air strike had killed 16 people in a building where Houthi rebels were gathering.
There were conflicting reports on the number of rebels versus civilians killed in the strike which was believed to have been carried out by the Saudi-led coalition.
The coalition said it was investigating the reports.
The strike occurred in the district of Al-Hali in Hodeida province, which is controlled by the Iran-backed insurgents.
The security sources said a second air strike targeted the house of a Houthi commander in the same area, but there were no immediate reports of casualties.
The rebels' Al-Masirah news outlet also reported two air strikes in Al-Hali district, saying they targeted a camp for displaced people and that most of the victims were women and children.
The security sources said there was no camp for the displaced in the area.
An AFP photographer saw children injured from a strike in the area being treated in hospital and medics collecting corpses at the scene.
The coalition is the only force known to carry out air strikes on Houthi rebel-held territory and has previously admitted to "erroneous" strikes that caused civilian casualties.
Saudi Arabia and its allies launched a military intervention in Yemen in 2015 with the aim of rolling back the Houthi rebels who had seized the capital and restoring the government to power.