Three children and more than 60 adults are reported to have been killed in air strikes in Yemen on Friday, Save the Children said, and a Reuters witness said several people including African migrants died in a raid in Houthi-held Saada province.
Rescue workers were still pulling bodies out of the rubble around midday following the dawn strike on the temporary detention center in Saada in north Yemen, but it was not immediately clear how many people had been killed.
A Saudi-led military coalition that has been fighting the Iran-aligned Houthi group since 2015 said the report would be fully investigated.
"We take this report very seriously and it will be fully investigated as all reports of this nature are, using an internationally approved, independent process. Whilst this is ongoing, it would be inappropriate to comment further," said coalition spokesman Brigadier-General Turki al-Malki.
The coalition has intensified air strikes on what it says are Houthi military targets after the group carried out an unprecedented assault on coalition member the United Arab Emirates on Monday and further missile and drones launches at Saudi cities.
A Save the Children statement said more than 60 adults were killed in air strikes in Yemen on Friday, adding three children were killed when missiles struck the western city of Hodeidah.
It called on parties to the conflict to protect children and their families from "the horror of the ongoing violence" and avoid the use of explosive weapons in populated areas.
Houthi-run Al Masirah television channel said tens of people had been killed and injured in the strike in Saada. It showed footage of men trying to clear rubble using their hands to reach those trapped and of wounded at al-Jamhuri hospital.
Despite Yemen's war, migrants from the Horn of Africa still go there en route to Saudi Arabia or wealthy Gulf states.
Yemen was experiencing a nationwide Internet outage on Friday with the exception of the southern city of Aden. Houthi media blamed it what it said was a coalition strike on a telecommunications facility in Hodeidah. Reuters could not immediately confirm the cause of the outage.
The Saudi-led alliance on Thursday reported operations against "Houthi military capabilities" in Hodeidah, ballistic missile launch platforms in Bayda province in central Yemen and military targets in Yemen's Houthi-held capital Sanaa.
The UN Security Council condemned the Houthi attack on the UAE and other sites in Saudi Arabia in a statement on Friday and "underlined the need to hold perpetrators, organizers, financiers and sponsors of these reprehensible acts of terrorism accountable and bring them to justice."
The statement came after the council met behind closed-doors to discuss the Houthi attack on the UAE, which requested the discussion. The UAE joined the 15-member council this month for a two-year term.
When asked about the air strikes on Yemen on Friday, UAE UN Ambassador Lana Nusseibeh told reporters: "The coalition undertake to abide by international law and proportionate response in all its military operations."
The conflict, in which the coalition intervened in March 2015 after the Houthis ousted the internationally recognized government from Sanaa, has killed tens of thousands of people, displaced millions and pushed Yemen to the verge of famine.