IRAQ -- More than 45,000 people have fled from western Mosul in recent weeks, as Iraqi forces backed by the U.S. military try to retake the city from the Islamic State of Iraq and Syria (ISIS). More than 200,000 people have been displaced in the battle over Iraq’s second-largest city.

On Sunday, there were reports of heavy clashes in western Mosul between U.S.-backed Iraqi forces and the ISIS militants they are trying to drive out of the city.

The extremists used at least six suicide car bombs, according to the Iraqi forces. Those are vehicles laden with explosives, and driven at high speed towards Iraqi troops. A new ISIS propaganda video shows them being deployed -- an improvised and deadly weapon that ISIS has relied on in the street-to-street fighting in Mosul.

Iraqi security forces launch a rocket against ISIS militants positions during clashes in the western side of Mosul, Iraq, Sunday, March 5, 2017. (AP Photo/Khalid Mohammed)

A still photo from video posted on a militant website July 5, 2014, purports to show the leader of the Islamic State of Iraq and Syria, Abu Bakr al-Baghdadi, delivering a sermon at a mosque in Iraq during his first public appearance. Militant video/AP

Twelve people -- including children -- are being treated for possible exposure to chemical weapons in Mosul over the last week. The International Committee for the Red Cross said their symptoms are consistent with those inflicted by a blister agent, including vomiting, coughing and blisters.

The battle to retake Mosul from ISIS began in October, two years after the extremists captured the city. ISIS was pushed out of the eastern half of Mosul in January. The fight for the western half began just over two weeks ago. Deadly clashes have already forced more 200,000 people from their homes in Mosul, according to the United Nations.

The fighting is now moving closer to the city’s historic center and to the mosque where ISIS leader Abu Bakr Al-Baghdadi preached in July 2014 -- declaring himself the leader of a so-called Islamic State.

That state is now in retreat -- under assault in both Iraq and Syria by local ground forces and U.S. coalition airstrikes; ISIS is losing territory and fighters.

Lt. General Stephen Townsend -- the top U.S. commander in Iraq -- recently predicted that ISIS would be defeated in both Mosul and Raqqa -- its stronghold in Syria -- within six months.