(CNN) ISIS is fighting back Tuesday after its stronghold, Falluja, was surrounded by Iraqi forces.
In a video released by Iraq’s Ministry of Defense, Iraqi Gen. Hamid al-Maliki announced Monday the city was encircled by Iraqi troops.
Iraqi forces, in conjunction with Iraqi and coalition air support, started the operation to retake the city Monday, an Iraqi military spokesman said, capturing some villages on the outskirts of Falluja.
The next step in the military’s plan is to push into the heart of the city and drive ISIS out, which may be the most dangerous part of the operation.
Meanwhile, the danger for innocent people caught in the middle intensifies. There are reports that hundreds of families are being used by ISIS as human shields in the center of Falluja, said Caroline Gluk, spokeswoman for the United Nations refugee agency in Baghdad.
The agency has also received reports of civilian casualties, deaths caused by heavy shelling, she said.
About 3,700 people — or more than 600 families — have fled Falluja over the past week, since the offensive to retake the city from ISIS began, according to the UNHCR.