U.S.-backed Iraqi forces said they began a push on Wednesday, June 21 toward the mosque of Mosul, where Islamic State declared a self-styled caliphate three years ago, Reuters says.

The military said the forces had encircled the jihadist group's stronghold in the Old City of Mosul, where the mosque is located, on Tuesday.

The battle for the Old City is becoming the deadliest in the eight-month old offensive to capture Mosul, Islamic State's de facto capital in Iraq.