The US said Saturday it would begin an "immediate review" of its support for the Saudi-led coalition in Yemen, after an attack on a funeral in the capital Sana'a killed more than 140 people.
"US security cooperation with Saudi Arabia is not a blank check," National Security Council spokesman Ned Price said, adding, "we have and will continue to express our serious concerns about the conflict in Yemen and how it has been waged."
The UN said more than 140 people were killed and over 525 were injured in the airstrike on a community hall where thousands of mourners were taking part in a funeral ceremony for the late father of pro-rebel Interior Minister Galal al-Rawishan.
Al-Rawishan survived the attack unharmed.
UN Under-Secretary-General for Humanitarian Affairs, Stephen O'Brien, described the attack as "horrendous and heinous" and said that the number of casualties was likely to rise.
"[The attack] highlights once again the disproportionate risk forcivilians when explosive weapons are used in urban areas," O'Brien added.
The dead included the governor of Sana'a, Abdel-Qader Helal, and other senior officials from the Houthi rebels, medical officials in Sana'a said.
A ruling rebel council condemned the attack and vowed revenge.
The Sana’a-based Higher Political Council called on its backers to take to the streets on Sunday to protest against what it called “this criminality.”
The Saudi-led alliance denied it had bombed the site.
“The Arab alliance did not carry out any operations in the site of the bombing,” the coalition said, according to Saudi-owned broadcaster Al Arabiya.
Sana'a has been under the Iran-allied Houthis' control since September 2014 amid an escalating power struggle between them and internationally recognized President Abd Rabu Mansour Hadi.
The conflict has taken a toll on Yemen's civilians.
In August, UN rights chief Zeid Ra'ad Al Hussein said in a report that 2,067 civilians were killed in Yemen between July 2015 and June 2016 - 1,259 of whom died in Saudi-led airstrikes.
Yemen's conflict has intensified since March 2015, when the rebels advanced on the southern city of Aden, prompting Saudi Arabia and fellow Sunni allies to start an air campaign in Yemen against the group.
Saudi Arabia fears that the mostly Shiite rebels will give its regional rival, Shiite Iran, a strategic foothold on the Arabian Peninsula.