Mass grave in Iraq holds '40 IS victims'

A mass grave in the Iraqi city of Ramadi has been found containing the remains of at least 40 people killed by the Islamic State, officials say.

A mass grave in the Iraqi city of Ramadi has been found containing the remains of victims of IS. (AAP)

Iraqi authorities have uncovered a mass grave in Ramadi containing at least 40 bodies apparently killed by Islamic State insurgents when they seized the city in May.

Footage posted on the Facebook page of the provincial police showed what appeared to be bodies in varying states of decay being pulled from a shallow grave in the capital of Anbar province which Iraq's military recaptured last month.

Police chief Major General Hadi Razij spoke in the video about the grave, and an adviser to the governor confirmed the images were authentic. Interior Ministry spokesman Brigadier General Saad Maan also confirmed the reports.

"We believe they were the last to fight #DAESH before #Ramadi fell in May 2015. Investigation ongoing," Anbar Governor Sohaib al-Rawi said in a tweet with a picture of body bags lying in a street.

IS overran Ramadi last year as the Iraqi army abandoned its posts for the second time in less than a year, setting back government efforts to push back the ultra-hardline Sunni militants.

The military, backed by US-led coalition air strikes, recaptured the city in December, but widespread destruction and explosives planted by the insurgents in streets and houses have prevented civilians from returning.

Several mass graves have been uncovered in areas retaken from IS, which imposes strict restrictions and harsh punishments on the millions of civilians living under its control.