The US-led coalition has killed at least 484 civilians in air strikes in Syria and Iraq the military has said.

There have been other claims of mass casualties from other airstrikes in Syria and Iraq with the Inherent Resolve task force saying 'it does everything possible to avoid civilian casualties and publishes all'.

It stressed only 0.27 percent of its 21,035 strikes since the operation began had produced "credible" civilian death reports.

Independent monitors say the death toll since the bombing campaign against Isis started in 2014 runs into the thousands, with transparency project Airwars claiming at least 3,800 civilians have been killed.

In a monthly report, CentCom said investigations finished into 16 incidents that resulted in 132 “unintentional civilian deaths”, bringing the total to 484.

In many of the incidents, CentCom said civilians “entered the target area after the munition was released”, reports the Independent.

“In each of the incidents, the investigation assessed that all feasible precautions were taken and the decision to strike complied with the law of armed conflict,” a spokesperson for CentCom said, adding that civilian casualties had occurred in less than 1 per cent of more than 21,000 strikes over the past three years.