In its report, Airwars - a London-based collective of journalists and researchers that use social media, eyewitness reports, and other sources to compile its data - said that the concurrent assaults on Mosul in Iraq and Raqqa in Syria were often "devastating."
The number is completely at odds with that of the US military, which so far has only acknowledged the accidental deaths of 603 civilians in the entire period since coalition operations began in late 2014.
The ongoing and deeply worrying increase in civilian deaths attributed to Coalition actions means that for six straight months, casualty incidents reportedly carried out by the US-led Coalition in Iraq and Syria have significantly outweighed those attributed to Moscow just in Syria. In June, this gap was greater than ever before - with nearly five times as many reported Coalition civilian casualty events as there were Russian -- Airwars
The report said that over 23,000 air and artillery strikes had reportedly been carried out by the coalition in Iraq (13,049) and Syria (9,971) since the start of the campaign.
Pentagon's goal placed civilians at risk
Airwars director Chris Woods said the increased tempo of strikes in Mosul and Raqqa accounted for some of the increase but suggested the Pentagon's goal of "annihilation" of Daesh militants had placed civilians at greater risk of harm.
"While it was always predicted that high civilian casualties would occur during the assaults on Raqqa and Mosul, this alone cannot explain the very high fatalities we and other monitors, NGOs and international agencies are tracking," Woods said.
International airstrikes and civilian casualty claims in Iraq and Syria: June 2017
Almost five times more Coalition than Russian civilian casualty allegations were tracked by Airwars during June
Amnesty International on Tuesday called for a commission to investigate crimes against civilians in Mosul by all sides in the battle to liberate the Iraqi city from Daesh.
The charity said that Iraqi and coalition forces had failed to take adequate measures to protect civilians.
Lieutenant General Stephen Townsend, who leads the anti-Daesh coalition, rejected such claims.
"This is, I believe, the most precise campaign in the history of warfare," Townsend said.
"I would challenge the people from Amnesty International, or anyone else out there who makes these charges, to first research their facts and make sure they're speaking from a position of authority."
The US military's Central Command is currently wading through a backlog of old Airwars claims and so far has assessed most of these to be "non-credible."
Coalition spokesman Colonel Ryan Dillon said that a seven-person team reviews every civilian casualty allegation, many of which are self-reported through the military itself.