A U.S. airstrike killed the Islamic State's commander in Fallujah, where the Iraqi army recently launched a major push to clear out the terror group, a Pentagon spokesman announced Friday.

The strike killed Maher al-Bilawi on Wednesday, Col. Steve Warren said from Iraq. "This was a result of intelligence that we gathered on the headquarters and his location. And we had the opportunity to take the strike and we took it."

Warren said he had few details on the commander's background, but added, "This cat wasn't part of the high-value individual list. This is some intelligence we developed locally. We worked it very rapidly. And we took an effective strike and scored one for the good guys."

Meanwhile, Iraqi troops reportedly pushed toward Fallujah from the south Friday, aiming to completely surround the militant hub.

"Our troops are now in the process of surrounding the city from all (sides)," said Lt. General Abdul-Wahab al-Saadi, the head of the counterterrorism forces' Fallujah operation. "By doing so, we will besiege the city of Fallujah in full. And then we will start storming city from several directions with new forces."

Fallujah is located 40 miles west of Baghdad.

Booby-trapped explosives and large numbers of civilians unable to escape were expected to complicate operations moving forward, al-Saadi said.

The spiritual leader of Iraq's Shiites called on Iraqi forces battling to retake the city of Fallujah to protect civilians there. Grand Ayatollah Ali al-Sistani said that "saving innocent people from harm's way is the most important thing, even more so than targeting the enemy."

His comments were delivered at Friday prayers by his representative, Ahmed al-Safi, in the holy city of Karbala.

Rights groups have expressed concerns for the tens of thousands of civilians estimated to still be in the city, which has been in ISIS hands for more than two years.

In the capital, Baghdad, Iraqi security forces fired tear gas and live ammunition to disperse thousands of anti-government protesters gathered in the city's Tahrir roundabout. The protesters assembled despite calls earlier this week from Iraqi Prime Minister Haider al-Abadi to halt protests so the country's security forces could focus on the Fallujah operation.

Fox News' Lucas Tomlinson and The Associated Press contributed to this report.