An Iraqi army airstrike in the militant-held northern city of Mosul on Wednesday, Aug 6, killed 60 fighters from the extremists Islamic State group, the Iraqi state television reported, according to the Associated Press.

The report said the dawn strike targeted a downtown prison that was being used by Islamic State members as a religious court and detention facility.

The AP says the claim could not be independently verified and the area was inaccessible to most media.

Sunni extremists from the al Qaeda-breakaway Islamic State group seized Mosul, Iraq's largest second-largest city, in a blitz offensive in June that also captured large swaths of the country's north and west.

The militant onslaught plunged Iraq into its worst crisis since the withdrawal of U.S. troops in 2011.

The group has since imposed a self-styled caliphate in territory it controls in Iraq and Syria, imposing the militants' harsh interpretation of Islamic law.

Since then, Iraqi government forces and allied Sunni tribal militiamen have been struggling to dislodge the militants but with no apparent progress.

The TV report said 60 militants were killed in Wednesday's strike and about 300 people who were in the militants' custody were set free. The report cited intelligence officials but provided no further information.

A Mosul resident, speaking on condition of anonymity fearing for his own safety, told the AP over the phone that families of the prisoners rushed to the site to help their kin.

"The prison was partly damaged in the airstrike," he said, adding that he did not know if there were casualties.