Coalition air strike on Manbij
Coalition air strike on ManbijReuters

The international coalition fighting the Islamic State (ISIS) group has opened a formal investigation to determine whether its air strikes last week near the Syrian city of Manbij claimed civilian lives, a spokesman said Wednesday, according to AFP.

The main Syrian opposition group last week urged the U.S.-led coalition to suspend its bombardments following the July 19 strikes, which a rights-monitoring group and local residents said had killed dozens of civilians.

After examining "internal and external information," the coalition determined that there was sufficient credible evidence of civilian victims to open a formal inquiry, spokesman Colonel Chris Garver said on Wednesday.

The Britain-based Syrian Observatory for Human Rights said at least 56 civilians, including 11 children, died as they fled from a village near Manbij, a strategic waypoint between Turkey and the jihadist stronghold of Raqa.

A death toll of that magnitude would appear to be the worst in nearly two years of coalition air strikes against ISIS targets.

Garver said Wednesday that death estimates from residents near Manbij ranged from a low of "10 to 15" to a high of 73.

Garver had earlier accused ISIS of using civilians as "human shields."

Coalition officials often say theirs is the most precise air campaign in history.

Nearly all coalition air strikes use guided munitions, involving laser or GPS systems, or else missiles. Targets are often viewed at length using surveillance drones before the order to attack is issued.

After the Manbij bombardment, Amnesty International urged the coalition to redouble its efforts to prevent civilian deaths and to investigate possible violations of international humanitarian law.

The London-based nongovernmental organization Airwars has estimated that the roughly 14,000 coalition bombing attacks since August 2014 have claimed at least 1,513 civilian lives.

The coalition has officially acknowledged only a few dozen civilian victims.

After the air strikes of July 19, the main Syrian opposition group, the Istanbul-based National Coalition, called on the U.S.-led forces to suspend bombardments.

The group's president, Anas al-Abdeh, said civilian casualties could heighten a sense of desperation among Syrians and provide a recruiting tool for extremist groups like ISIS.

Garver said last week that the jihadists had been mounting exceptionally fierce resistance in Manbij.

"It's a fight like we haven't seen before," he said.

AFP contributed to this report.