The Operation Inherent Resolve coalition added 132 civilians to the total in its April report, including 105 who died when a US aircraft dropped a bomb on an IS sniper target in west Mosul on March 17.
The bomb inadvertently set off a large cache of explosives, collapsing a building on top of civilians sheltering below.
The Inherent Resolve task force "takes all reports of civilian casualties seriously and assesses all reports as thoroughly as possible," the US-led task force said in a monthly statement.
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It stressed only 0.27 percent of its 21,035 strikes since the operation began had produced "credible" civilian death reports.
The total reported Friday was still far short of what non-governmental organizations estimate for civilian deaths in the conflict in Iraq and Syria.
Airwars, a journalist collective based in London that compiles data from public sources, estimated more than 3,800 non-combatants were killed since the operations began in August 2014.
The Syrian Observatory for Human Rights estimates that in the month from April 23 to May 23, 225 civilians were killed in Syria alone, the heaviest monthly toll since 2014.
The official report Friday only covers reported incidents through the end of April.