Civilian deaths and injuries in Yemen's civil war have almost doubled since UN human rights monitors were controversially removed in October, a non-governmental organisation said on Thursday.
The ejection of monitors had opened the door to "unchecked, horrific violations", the Norwegian Refugee Council said, urging their reinstatement.
It said 823 civilians were killed or injured in the four months before the end of monitoring, and 1,535 in the four months after their departure.
The report added that civilian casualties caused by air strikes, a tactic favoured by the Saudi-led coalition battling Iran-backed Huthi rebels, had multiplied by 39 in the same period.
"The removal of this crucial human rights investigative body took us back to unchecked, horrific violations," country director Erin Hutchinson said in a statement.
"Who is responsible for the deaths of these children and families? We will probably never know because there is no longer any independent, international and impartial monitoring of civilian deaths in Yemen."
The UN Human Rights Council voted to disband its Group of Eminent International and Regional Experts on Yemen in October, in a move that was strongly criticised by human rights groups.
It was the first time that the United Nations' top rights body had rejected a draft resolution since it was founded in 2006. The resolution, brought forward by European nations and Canada, was defeated by 21 votes to 18.
"The people of Yemen have been abandoned. Betrayed. Yet again," Amnesty International's secretary general Agnes Callamard said at the time.
Hundreds of thousands of people have been killed directly or indirectly in Yemen's seven-year war, while millions have been displaced in what the UN calls the world's biggest humanitarian crisis.
"The UN member states should urgently reinstate the monitoring body to ensure that parties to the conflict stop committing grave breaches of international humanitarian law with impunity," Hutchinson said.
"With no one to hold perpetrators accountable, civilians will continue to be killed by the thousands and (to be) the hardest hit by the escalation of the conflict."