About 151,000 Iraqi civilians were killed in the three years following the US-led invasion of their country, according to World Health Organisation (WHO).
The new study said violent deaths could have ranged from 104,000 to 223,000 between March 2003 and June 2006.
The study drew on an Iraqi health ministry survey of nearly 10,000 households - five times the number of those interviewed in a disputed 2006 John Hopkins University study that said more than 600,000 Iraqis had died over the period.
Although well below that figure, the United Nations agency's estimate exceeds the widely cited 80,000 to 87,000 death toll by the human rights group Iraq Body Count, which uses media reports and hospital and morgue records to calculate its tally.
WHO statistician Mohamed Ali, who co-authored the study, said insecurity made parts of Baghdad and Anbar provinces unreachable for those conducting the survey, which included questions about other topics including pregnancy and disease.
Many families also fled their homes as a result of the violence, and some left the country, making it hard to give a precise assessment of the violence in Iraq.
The John Hopkins University report, published by the British medical journal Lancet, which was based on a smaller-scale Iraqi survey, drew criticism from the White House and elsewhere for appearing to exaggerate the Iraqi death rate.
Iraqi Health Minister Saleh al-Hasnawi described the latest WHO report as "very sound" and said the survey indicated a massive death toll since the beginning of the conflict.
More than half of the violent deaths documented in the WHO report occurred in Baghdad, while an average of 128 Iraqis suffered violent deaths every day in the first year following the invasion. The next year, an average of 115 were killed daily and 126 died from violence each day in the third year after the war started.