Yemeni media reported that 22 civilians were killed when Saudi warplanes targeted displaced families in Mawza’ District in the southwestern province of Ta’izz on July 18.
The UN human rights office, which reported 18 civilian deaths in the attack, said in a statement the raids hit three families who were staying in a makeshift straw house after being forced to flee from their homes three months ago.
The office said in a statement that the attack was carried out by "Arab Coalition Forces", referring to the so-called Saudi-led military alliance, which has been engaged in a deadly campaign against Yemen since March 2015.
"There do not appear to have been any military objectives anywhere in the immediate vicinity of the destroyed house," the statement said.
The UN also urged a "comprehensive and impartial investigation" into the strike.
Saudi Arabia has been leading the campaign against Yemen to reinstate the former government and crush the Houthi Ansarullah movement.
The campaign has seriously damaged the country's infrastructure. Local Yemeni sources have put the death toll from the Saudi war at over 12,000, including many women and children.