US-led strikes against ISIS have killed at least 352 civilians

Coalition strikes against ISIS in Iraq and Syria have likely killed at least 352 civilians since the start of the operation almost three years ago, the US military said Sunday.

The numbers, contained in the monthly civilian casualty report of the Combined Joint Task Force-Operation Inherent Resolve, extend through March.

Inherent Resolve is the US-led assault against the Islamic State that kicked off in August 2014.

"We regret the unintentional loss of civilian lives resulting from Coalition efforts to defeat ISIS in Iraq and Syria and express our deepest sympathies to the families and others affected by these strikes," the task force said in a statement.

The 352 deaths mark a significant increase over the 229 civilian deaths that were counted through the end of February.

The latest report cited 45 newly confirmed deaths in nine new reports from November through March. It also cited 80 civilian deaths that hadn't been announced before. An audit concluded that previously incorrect reporting resulted in a "net reduction of two deaths."

The military also said 42 reports of civilian casualties remain under review, including several last month in Mosul where there have been reports of many civilian deaths.

Seventeen new civilian casualty reports were deemed not credible. The coalition has made more than 20,000 strikes through March 2017.

Commanders want to prevent civilian casualties.

"I think the principal way that we are addressing this is by entrusting and enabling our very well-experienced and trained leaders on the ground. They are the best guard against this," Gen. Joseph Votel, commander of US Central Command, told lawmakers at a recent congressional hearing.

The US military says it works to review civilian death reports even though it is unable to probe all reports with "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 task force said.

Monitoring groups such as Airwars have issued higher civilian death estimates than the Pentagon.