MOSUL, Iraq (AP) — The United Nations says the fight for Mosul in Iraq is causing higher numbers of displaced people than previously seen in the 4 ½-month-long operation.

The U.N. says in a statement that 28,400 people have been forced from their homes since the operation began more than a week ago.

The statement released Wednesday adds that since Feb. 25, some 4,000 people have fled the city each day.

The push to retake western Mosul began last msonth after the eastern half of the city was declared "fully liberated" in January. The operation to retake Mosul from the Islamic State group was formally launched in October.

The offensive came after the militants were pushed out of most of the territory they controlled in Iraq after overrunning the north and west in the summer of 2014.