The rights group said it expects up to 5,000 digital activists to sign up for the month-long project researching the destruction of almost 80 percent of the former jihadist bastion.

Amnesty said evidence collected in field investigations since the end of the 2017 battle had led the US-led coalition to revise its civilian death toll from 23 to 100.

"But with bodies still being recovered from the wreckage and mass graves more than a year later, this is just the tip of the iceberg," said Amnesty's Milena Marin.

"There is a mountain of evidence left to sift through, and the scale of the civilian devastation is simply too large for us to do this alone," she said.

The "Strike Tracker" project will enlist thousands of volunteers to sift through timelines of satellite imagery and track the destruction caused by air strikes.

The coalition rained missiles on Raqa, once the de facto Syrian capital of the Islamic State group's self-proclaimed "caliphate", to help Kurdish-led forces on the ground retake the city.

Victory against the jihadists was declared in October 2017.

Amnesty said the crowdsourcing drive would help assess the impact on civilians who were trapped inside Raqa during the air strikes.

It also hoped to "move the US-led coalition's position on civilian casualties from ongoing denial to accepting greater responsibility and carrying out meaningful investigations".

"The coalition's blatant denials and shoulder-shrugging are unconscionable -- their military offensive killed and maimed hundreds of civilians and then left the survivors to pick up the pieces," Marin said.

For its project, Amnesty is partnering with Airwars, an organisation that assesses the harm caused to civilians by airpower in various conflicts.