US and Russian-backed forces have killed at least 19,663 non-combatant civilians in Syria and Iraq between August 2014 and July 2017, monitoring group Airwars estimates.
The London-based collective of journalists and researchers say that at least 7,337 death were caused by the US-backed coalition in this region.
The numbers the non-profit provided are subject to caution given the challenges of verification in the area, but are based on reports from international and local news agencies, NGOs, social media reports and video footage.
The news comes as US-led forces in Syria claimed another 21 civilian lives on Friday.
"To date, based on information available, (the coalition) assesses that, it is more likely than not, at least 624 civilians have been unintentionally killed by coalition strikes" since the anti-Daesh campaign began in late 2014, the US-backed Coalition said, offering numbers from internal investigations, diverging from the international non-profit.
Among the incidents the coalition said resulted in casualties was a May 12 strike near Raqqa that targeted Daesh but also killed 10 civilians in a nearby building.
"Although all feasible precautions were taken and the decision to strike complied with the law of armed conflict, unintended civilian casualties unfortunately occurred," the statement read.
"45 percent" of Raqqa under SDF control
US-backed SDF group battling to recapture Raqqa from the Daesh has now seized about 45 percent of the terrorist group's de-facto capital in Syria, a top US official said Friday.
The SDF began a campaign to capture Raqqa from Daesh last year, slowly encircling the city before breaking into it for the first time in June.
The SDF is dominated by YPG, which is the armed wing of the PYD, the main partner for the US-led coalition against Daesh in Syria. The US decision to arm the YPG/PYD has incensed NATO ally Turkey, as it considers the group to be the Syrian branch of the PKK.
The PKK is recognised as a terrorist group by Turkey, the US and EU.
"As of today, the SDF has seized about 45 percent," of Raqqa, said Brett McGurk, the senior US envoy to the international coalition fighting Daesh in Iraq and Syria.
The recapture of Raqqa would mark a major milestone in the three-year effort to defeat Daesh.
The terrorist group was ousted from its main Iraqi bastion of Mosul last month.
McGurk said Daesh has lost 27,000 square miles (70,000 sq km) of the territory it once held in the two countries - 78 percent of what they had seized in Iraq and 58 percent of what they held in Syria.
Still, the Raqqa battle is far from over, with thousands of Daesh fighters remaining.
"I'm always hesitant to give numbers like that because this is an inexact science, but we think there's about 2,000 fighters left in Raqqa -- and they most likely will die in Raqqa," McGurk said.
The United Nations estimates between 20,000 to 50,000 civilians may still be in the city, though other estimates are lower.
US, France discuss increasing cooperation in Syria and Iraq
US President Donald Trump discussed increasing cooperation in the ongoing crises in Syria and Iraq in a telephone call with his French counterpart Emmanuel Macron on Friday.
The two leaders also spoke about "countering Iranian malign influence," according to a readout of the call provided by the White House.
The two leaders spoke in the backdrop of rising tensions between the US and Russia following US sanctions on Russia earlier this week.
President Donald Trump said on Thursday the US-Russian relationship was at "an all-time and very dangerous low," and Russia said new sanctions imposed by Washington meant an end to hopes for better ties with the Trump administration.
McGurk said "deconfliction" arrangements the US and Russian militaries have made to avoid accidents as they operate separately in Syria were working well despite deteriorating diplomatic relations between the two countries.
"So far we have not seen an effect on our engagement with the Russians when it comes to Syria," McGurk said.