LONDON - Researchers have estimated that as many as 100,000 more Iraqis - many of them women and children - died since the start of the U.S.-led invasion of Iraq than would have been expected otherwise, based on the death rate before the war.

Writing in the British-based medical journal The Lancet, the American and Iraqi researchers concluded that violence accounted for most of the extra deaths and that airstrikes by the U.S.-led coalition were a major factor.

There is no official figure for the number of Iraqis killed since the conflict began, but some non-governmental estimates range from 10,000 to 30,000. As of Thursday, 1,106 U.S. servicemen had been killed, according to the U.S. Defense Department.

The scientists who wrote the report concede that the data they based their projections on were of "limited precision," because the quality of the information depends on the accuracy of the household interviews used for the study. The interviewers were Iraqi, most of them doctors.

Designed and conducted by researchers at Johns Hopkins University, Columbia University and the Al-Mustansiriya University in Baghdad, the study was published Thursday on The Lancet's Web site.

The survey attributed most of the extra deaths to violence and said airstrikes by coalition forces caused most of the violent deaths.

"Most individuals reportedly killed by coalition forces were women and children," the researchers wrote.

The report was released just days before the U.S. presidential election, and the lead researcher said he wanted it that way. The Lancet routinely publishes papers on the Web before they appear in print, particularly if it considers the findings of urgent public health interest.

Those reports then appear later in the print issue of the journal. The journal's spokesmen said they were uncertain which print issue the Iraqi report would appear in and said it was too late to make Friday's issue, and possibly too late for the Nov. 5 edition.

Les Roberts, the lead researcher from Johns Hopkins, said the article's timing was up to him.

"I emailed it in on Sept. 30 under the condition that it came out before the election," Roberts told The Associated Press. "My motive in doing that was not to skew the election. My motive was that if this came out during the campaign, both candidates would be forced to pledge to protect civilian lives in Iraq.

"I was opposed to the war and I still think that the war was a bad idea, but I think that our science has transcended our perspectives," Roberts said. "As an American, I am really, really sorry to be reporting this."

Richard Peto, an expert on study methods who was not involved with the research, said the approach the scientists took is a reasonable one to investigate the Iraq death toll.

However, it's possible that they may have zoned in on hotspots that might not be representative of the death toll across Iraq, said Peto, a professor of medical statistics at Oxford University in England.

 Lancet editor Richard Horton wrote in an editorial accompanying the survey that more household clusters would have improved the precision of the report, "but at an enormous and unacceptable risk to the team of interviewers."

"This remarkable piece of work represents the efforts of a courageous team of scientists," he wrote.

To conduct the survey, investigators visited 33 neighborhoods spread evenly across the country in September, randomly selecting clusters of 30 households to sample. Of the 988 households visited, 808, consisting of 7,868 people, agreed to participate. Each household was asked how many people lived in the home and how many births and deaths there had been since January 2002.

The scientists then compared death rates in the 15 months before the invasion with those that occurred during the 18 months after the attack and adjusted those numbers to account for the different time periods.

Even though the sample size appears small, this type of survey is considered accurate and acceptable by scientists and was used to calculate war deaths in Kosovo in the late 1990s.

The investigators worked in teams of three. Five of the six Iraqi interviewers were doctors and all six were fluent in English and Arabic.

In the households reporting deaths, the person who died had to be living there at the time of the death and for more than two months before to be counted. In an attempt at firmer confirmation, the interviewers asked for death certificates in 78 households and were provided them 63 times.

There were 46 deaths in the surveyed households before the war. After the invasion, there were 142 deaths. That is an increase from 5 deaths per 1,000 people per year to 12.3 per 1,000 people per year - more than double.

However, more than a third of the post-invasion deaths were reported in one cluster of households in the city Fallujah, where fighting has been most intense recently. Because the fighting was so severe there, the numbers from that location may have exaggerated the overall picture.

When the researchers recalculated the effect of the war without the statistics from Fallujah, the deaths end up at 7.9 per 1,000 people per year - still 1.5 times higher than before the war.

Even with Fallujah factored out, the survey "indicates that the death toll associated with the invasion and occupation of Iraq is more likely than not about 100,000 people, and may be much higher," the report said.

The most common causes of death before the invasion of Iraq were heart attacks, strokes and other chronic diseases. However, after the invasion, violence was recorded as the primary cause of death and was mainly attributed to coalition forces - with about 95 percent of those deaths caused by bombs or fire from helicopter gunships.

Violent deaths - defined as those brought about by the intentional act of others - were reported in 15 of the 33 clusters. The chances of a violent death were 58 times higher after the invasion than before it, the researchers said.

Twelve of the 73 violent deaths were not attributed to coalition forces. The researchers said 28 children were killed by coalition forces in the survey households. Infant mortality rose from 29 deaths per 1,000 live births before the war to 57 deaths per 1,000 afterward.

 The researchers estimated the nationwide death toll due to the conflict by subtracting the preinvasion death rate from the post-invasion death rate and multiplying that number by the estimated population of Iraq - 24.4 million at the start of the war. Then that number was converted to a total number of deaths by dividing by 1,000 and adjusting for the 18 months since the invasion.

"We estimate that there were 98,000 extra deaths during the postwar period in the 97 percent of Iraq represented by all the clusters except Fallujah," the researchers said in the journal.

"This isn't about individual soldiers doing bad things. This appears to be a problem with the approach to occupation in Iraq," Roberts said.

The researchers called for further confirmation by an independent body such as the International Committee of the Red Cross, or the World Health Organization.

The study was funded by the Center for International Emergency Disaster and Refugee Studies at Johns Hopkins University and by the Small Arms Survey in Geneva, Switzerland, a research project based at the Graduate Institute of International Studies in Geneva.

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