Yemen's Houthi rebels say an alleged United States airstrike on a prison holding African migrants in Saada province has killed at least 68 people.
Saada is a Houthi stronghold that has also been previously targeted in US strikes.
According to Yemen's interior ministry, the detention centre was housing 115 African migrants.
Houthi-run Al Masirah television showed images of the aftermath of the strike in Saada, on a route used by African migrants to cross impoverished, conflict-riven Yemen to reach Saudi Arabia.
The footage showed bodies covered in dust amid blood-stained rubble.
Rescue workers carried a man who was moving slightly on a stretcher. A survivor could be heard calling "My mother" in Amharic, the main language of Ethiopia.
The American administration had committed a "brutal crime" by bombing the Saada detention centre which held more than 100 undocumented African migrants, Houthi spokesperson Mohammed Abdulsalam said on X.
Rights advocates have raised concerns about civilian killings. In the US, three Democratic senators wrote to defence secretary Pete Hegseth last week, demanding an accounting for the loss of civilian lives.
United Nations spokesperson Stéphane Dujarric said on Monday: "Strikes pose a growing risk to the civilian population in Yemen."
"We continue to call on all parties to uphold their obligations under international humanitarian law, including the protection of civilians."
Why is the US targeting the Houthis?
US President Donald Trump has intensified military operations targeting Iran-backed Houthi forces, conducting the deadliest strike thus far earlier this month on a fuel terminal on the Red Sea that killed at least 74 people.
The US has pledged to continue its attacks on the Houthis until they cease assaults on Red Sea shipping.
The Houthis, who have seized significant territory in Yemen over the past decade, have launched numerous drone and missile attacks on Red Sea vessels since November 2023, claiming they are targeting ships associated with Israel in support of Palestinians amid the conflict in Gaza.
US Central Command defends policy
In a statement before news of the alleged strike, the US military's Central Command sought to defend its policy of offering no specific details of its extensive airstrike campaign.
"To preserve operational security, we have intentionally limited disclosing details of our ongoing or future operations," Central Command said. "We are very deliberate in our operational approach, but will not reveal specifics about what we've done or what we will do."
Yemen has witnessed civil war for a decade between the Houthis and a government that controls the south, backed by Arab states, although fighting had eased for the past two years following a truce between the Houthis and Saudi Arabia.
Hundreds of thousands of people seeking to escape poverty travel through the Horn of Africa and across the Red Sea each year, then journey on foot through Yemen to the Saudi border, aid agency officials say.
More than 500 people drowned crossing the Red Sea last year as they tried to reach Yemen, according to the International Organization for Migration, a UN agency.
