Tens of thousands of trapped Iraqi civilians have stalled the government's advance in the battle against the Islamic State group in the western Anbar province, the spokesman for Iraq's elite counterterrorism said Friday.

The civilians are trapped between the Iraqi forces' lines and the IS extremists hunkered down in the center of the town of Hit, 85 miles west of Baghdad, the official told The Associated Press.

Meanwhile, IS claimed responsibility for two suicide car bombings that killed 11 security forces late Thursday night southeast of the city of Mosul, which is controlled by IS.

Early Thursday morning, Iraqi forces re-launched an offensive on Hit under cover of heavy U.S.-led coalition airstrikes, said the counterterrorism chief, Sabah al-Numan. Over the past week the coalition launched 17 airstrikes in and around Hit, according to Pentagon statements.

The town lies along an IS supply line linking the extremist group's fighters in Iraq and those in neighboring Syria. Iraqi commanders have said that retaking the town would be key to building on their momentum after retaking the Anbar provincial capital of Ramadi earlier this year and linking up government forces to the west and the north of Baghdad in preparation for an eventual push on Mosul.

The counterterrorism forces, which are leading the Hit operation, reached within 1.8 miles of Hit center Thursday before being forced to stop, al-Numan said.

"The commanders are making a plan to evacuate these families," al-Numan said, Iraqi forces dropped leaflets over Hit, telling civilians which roads they can take to flee safely.

Iraqi forces encountered similar problems in the battle for Ramadi earlier this year — as government forces advanced across downtown Ramadi, IS pulled back and took civilians captive, significantly slowing the advance of ground troops. While downtown Ramadi was declared under government control in December 2015, it wasn't until two months later that Iraqi and coalition forces said the rest of the city was "fully liberated."

One of the IS car bombings southeast of Mosul killed eight Iraqi Kurdish fighters while the other targeted an Iraqi police station in the same area, killing three policemen.

Iraq's military is conducting what the U.S.-led coalition describes as "shaping" operations ahead of a planned Mosul offensive. Iraqi forces have pushed IS out of a number of villages around Makhmour base where a U.S. Marine was killed during an IS attack last month.

On Wednesday, Iraqi forces celebrated as they took the Anbar provincial town of Kubaisa from IS.

Makhmour base and other front-line Iraqi positions southwest of Mosul have increasingly come under attack from IS in recent weeks as Iraqi troops built up in the area.

After storming across Iraq in the summer of 2014 and overrunning Mosul, the Islamic State group still controls large swaths of territory in the country's north and west.