(CNN) - Iraqi forces said Thursday they had retaken the city center of Hawija, one of the last major ISIS strongholds in Iraq.
It was not immediately clear how much of Hawija remained under ISIS control. Operations were continuing, Lt. Gen. Abdul Amir Rasheed Yarallah, commander of the Iraqi Joint Forces, said in a statement.
The offensive began on September 21.
"Our Iraqi partners fought bravely and professionally against a brutal and determined enemy, safeguarding innocent civilians throughout the entire campaign," Lt. Gen. Paul E. Funk II, commanding general of the Combined Joint Task Force -- Operation Inherent Resolve -- said in a statement Thursday.
"Today's victory demonstrates we are stronger together, and this Coalition remains committed to supporting our partners in the tough fight ahead as we continue our mission to defeat ISIS," he added.
Iraqi security forces are conducting operations in Western Anbar province, while the towns of Anah, Rayhanah and Akashat have all been secured, the statement said.
On Tuesday, the UN's Office for the Coordination of Humanitarian Affairs (OCHA) spokesman Jens Laerke said up to 78,000 civilians could be trapped by ISIS in the northern Iraqi city. Laerke said at least 12,500 people had fled the fighting.
The Norwegian Refugee Council, which says it has been working with families fleeing Hawija since October 2015, says many refugees have been left displaced with no homes to return to.
"No one must be forced to return to the newly retaken areas," said the NRC's country director in Iraq, Heidi Diedrich. "It is crucial for Iraq's future that all returns are informed, voluntary and happen only after areas are safe and basic services can be provided."
ISIS has been losing ground in Iraq since US-backed Iraqi forces captured the group's stronghold of Mosul in July after an intense nine-month battle.
In August, ISIS was driven out of Tal Afar, a northwestern town captured by the terror group in June 2014.
This story has been updated to clarify the significance of Hawija.