WASHINGTON — Facing mounting pressure over civilian casualties in American airstrikes, the United States-led coalition fighting the Islamic State in Iraq and Syria said on Saturday that it was likely that at least 229 civilians had been unintentionally killed since the start of the operations in August 2014.
In February, the last month covered by the report and the first full month of the Trump administration, four such civilians were killed, the coalition said. The assessment, issued monthly, does not include the March 17 strike against a building in Mosul in which scores if not hundreds of civilians were killed, according to Iraqi witnesses. That strike is under investigation.
The coalition’s overall count is far less than estimates by some human rights groups. Airwars, a nongovernment organization that monitors reports of civilian casualties in international airstrikes, has asserted that at least 2,831 civilians are likely to have been killed by the coalition’s air attacks since August 2014.
The worries about civilian casualties have grown as Iraqi forces push to take western Mosul from the Islamic State with the help of American and allied air power, rockets and artillery. President Trump has vowed to step up the fight against the militants, though the basic strategy in Mosul was set by American commanders during the Obama administration.
“We take the issue of civilian casualties seriously, every day, not just when it makes news,” said Col. John J. Thomas, the spokesman for the United States Central Command, which oversees American military operations in the Middle East. Colonel Thomas added that the command, in an effort to be “fully transparent,” was sharing information on unresolved cases and was even describing episodes that military personnel had reported up the chain of command but had not previously received public attention.
Chris Woods, the director of Airwars, asserted that while the Central Command had been working to improve its casualty counts, it was still lagging behind. “Certainly, both Centcom and the coalition have put a lot of effort into improving their casualty monitoring process, and we have been in extensive dialogue with them,” Mr. Woods said in a telephone interview from London.
“But despite these improved resources, both Centcom and the coalition appear unable to keep up with the number of allegations,” Mr. Woods added. “Given the intensity of operations in Mosul and around Raqqa, that gap continues to grow.” Raqqa, in Syria, is the Islamic State’s self-declared capital.
In western Mosul, hundreds of thousands of civilians are trapped, and airstrikes are an essential part of the operation. The Iraqi military has suffered enormous casualties — 284 Iraqi troops were killed during the first 37 days of the offensive to take western Mosul — and it depends on American firepower to advance. American military officials also allege that Islamic State fighters have herded Iraqi residents into buildings, calculating that escalating civilian casualties would prompt American commanders to slow the pace of airstrikes.
But critics say that the firepower that is being applied is so extensive that civilians are being put in danger. During a recent week in Mosul, the United States-led coalition carried out attacks with 700 bombs and rockets and another 400 strikes with satellite-guided Himars missiles, according to military officials.
With the United States unwilling to play a major ground combat role in Iraq and Syria, air power has become increasingly important. Between August 2014 and February 2017, the American-led coalition carried out 18,645 strikes. According to data made public by the command on Saturday, there were 37 reports of possible civilian casualties related to the operation to evict the Islamic State from the eastern half of Mosul, which began in mid-October. But 12 of these were deemed upon investigation to be “noncredible,” sometimes because no coalition strikes had been carried out in the area.
In five cases, the command found that the reports of civilian casualties were “credible.” In a Feb. 16 strike on a site that the military said was being used to make or hide an Islamic State car bomb, two civilians were killed when they entered the target area after the munition was released.
Forty-three cases of possible civilian casualties are still being assessed, including an April 2015 strike near Mosul. That case was reopened after new information was received.
In the March 17 strike in western Mosul, which led to the collapse of the building, American officials have acknowledged that the United States had a role, but said that the munition used should not have been powerful enough to bring down a building. They are examining whether the American strike might have set off a larger blast from explosives set by militants in or near the building.