The Pentagon said more than 350 civilians have been killed as a result of U.S. airstrikes against the Islamic State in Iraq and Syria (ISIS) in those two nations from August 2014 to March 2017.

“We regret the unintentional loss of civilian lives ... and express our deepest sympathies to the families and others affected by these strikes,” the Pentagon said in a statement on Sunday.

“All feasible precautions were taken,” the statement continued.

Pentagon investigations conducted in March revealed that coalition airstrikes had killed 45 civilians in and around the city of Mosul in Iraq, the Pentagon added.

The U.S. launched a campaign of airstrikes against ISIS in August of 2014, after it overran Mosul and swaths of Iraq's north and west territory.

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The Combined Joint Task Force has conducted 20,205 strikes in total.

Some of the death reported have been deemed "non-credible" because a lack of sufficient information needed to assess the cause of death, the Pentagon said.

The death tally by the U.S. military is lower than other as counted by outside groups.

Airwars, a journalist-led monitoring group, estimates 3,164 civilian deaths as a result of coalition air strikes, although their estimates also include civilian deaths in Libya, as well as in Iraq and Syria.

Reports from late last month say as many as 200 civilians were killed in Mosul from just one strike.

The airstrike operations first began in 2014.

Updated: 1:54 p.m.