The rights office has been mandated to track civilian casualties in Yemen since the start of the Saudi-led offensive in support of the government against an alliance of Iran- backed Huthi rebels and ex-president Yemeni Ali Abdullah Saleh.
"Between March 2015... And 30 August, at least 5,144 civilians have been documented as killed and more than 8,749 injured. Children accounted for 1,184 of those who were killed," the rights office said in a statement.
"Some 3,233 of the civilians killed were reportedly killed by Coalition forces."
More than 8,400 people, including civilians and combattants, are believed to have died in Yemen's civil war, according to UN estimates.
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The United Nations human rights chief, Zeid Ra'ad Al Hussein, has repeatedly pushed for an international investigation into violations in Yemen.
That effort has largely been stymied by Saudi pressure within the Human Rights Council, the UN body empowered to set up major international probes.
The rights office again cast doubt on the credibility of that probe, noting that it is "not perceived to be impartial."
"An international investigation would go a long way in putting on notice the parties to the conflict that the international community is watching and determined to hold to account perpetrators of violations and abuses," Zeid said in the statement.