The U.S.-led coalition fighting the Islamic State in Iraq and Syria (ISIS) has killed at least 603 civilians since the start of the campaign, the coalition said Friday in its latest monthly casualty report.

The new report’s totals include assessments of reports received from Airwars, a prominent independent monitor that places the number of civilians killed by the coalition at 4,354.

In all, the coalition in May evaluated 141 reports of civilian causalities and found 119 civilian deaths.

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The coalition “takes all reports of civilian casualties seriously and assesses all reports as thoroughly as possible,” the report said.

“Although we are unable to investigate all reports of possible civilian casualties using traditional investigative methods, such as interviewing witnesses and examining the site, the coalition interviews pilots and other personnel involved in the targeting process, reviews strike and surveillance video if available, and analyzes information provided by government agencies, non-governmental organizations, partner forces, and traditional and social media.”

The coalition found 70 reports from Airwars between 2014 and May 2016 to be “non-credible” for reasons including lack of sufficient evidence, no coalition strike occurring the in the area where the report originated or insufficient information in the report to evaluate its credibility.

“Worth noting coalition adds further 70 events tracked by Airwars which it presently assesses as 'not credible' - some of which we contest,” Airwars said in a tweet Friday.

4) Worth noting Coalition adds further 70 events tracked by Airwars which it presently assesses as 'not credible' - some of which we contest pic.twitter.com/kaWqhGzugh — Airwars (@airwars) July 7, 2017

Meanwhile, the coalition found 10 reports from Airwars to be credible, accounting for 44 civilian deaths and 27 injuries.

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On top of the Airwars reports, the coalition found 44 reports of civilian casualties from February through May to be non-credible.

The coalition also found 17 other reports of civilian casualties to be credible. Twelve of those happened in Mosul, underscoring the danger that civilians face in the dense urban streets where forces are seeking to drive out ISIS.

In cases where there were civilian casualties, the coalition said, the investigations found that “all feasible precautions” were taken and the strikes complied with the laws of armed conflict.

“Although the coalition takes extraordinary efforts to strike military targets in a manner that minimizes the risk of civilian casualties, in some incidents casualties are unavoidable,” the coalition said.