Islamic State has reportedly seized al-Baghdadi, in Iraq’s Anbar Province, 5 miles from an air base staffed by U.S. Marines, as the terror group continues its push beyond its bases in Syria and Iraq in an attempt to establish militant affiliates in other countries.

Hundreds of Islamic State fighters reportedly captured most of al-Baghdadi, which is 55 miles from the capital Ramadi, on Thursday.

On Friday, Iraqi soldiers had retaken several government buildings, but the soldiers withdrew early Saturday, handing the town back to the militants, The New York Times reported, citing local security officials.

One local Iraqi official told Reuters that, "Ninety percent of al-Baghdadi district has fallen under the control of the insurgents."

Militants attacked the town of al-Baghdadi from two directions before advancing inward, Reuters reported.

According to the Pentagon, al-Baghdadi was the first territorial gain by the militant group in months.

On Sunday, a U.S. Central Command spokesman refuted reports that ISIS had taken al-Baghdadi. "Al-Baghdadi has not fallen to ISIL or been seized by them," said U.S. Central Command, in an email to Fox News. Al-Baghdadi is "contested" not "Daesh held," said the email, referring to ISIS as Daesh, the name used by Arab partners to refer to the terrorist group.

On Friday, following the attack on al-Baghdadi, Islamic state fighters led a suicide attack on the Ayn al-Asad air base, where U.S. Marines are training Iraqi troops.

Most of the Islamic State fighters died in the suicide attack, killed either by Iraqi government forces or by detonating their suicide vests, said Navy Rear Adm. John Kirby, the Pentagon spokesman.

Kirby said an estimated 20-25 Islamic State militants were involved in the attack on al-Asad air base in Iraq's Anbar province. He said the attack was led by "at least several" suicide bombers, some of whom managed to detonate their bombs, while others were killed by Iraqi troops.

It appeared that most, if not all, of the militants were wearing Iraqi uniforms, Kirby said.

No Iraqi or U.S. troops were killed or wounded, Kirby said, and no U.S. troops were involved in the gunfight.

“This isn't the flu,” Rep. Peter King, R-N.Y., told Greta Van Susteren during “On The Record” Friday. “The fact is those 300 Marines [at al-Asad] are the toughest guys around. And they are well-armed. But the fact that the ISIS attack today didn't work doesn't mean that it couldn't work in the future,” said King.

“We have been given a warning signal, and we must take action.”

- Air Force Lt. Gen. Tom McInerney

Air Force Lt. Gen. Tom McInerney says the United States must use force in the area, seizing control of the key roads Islamic State, also known as ISIS, will need to continue its march toward the capital.

“We have been given a warning signal, and we must take action,” McInerney (Ret.) told Fox News Sunday. “The best defense is a good offense.”

A Defense Department spokeswoman confirmed to Fox News that “heavy fighting” took place in the area on Thursday, but referred questions about the status of al-Baghdadi to the Iraqi government.

“There was no direct attack on the al-Asad air base,” the spokeswoman assured, while acknowledging reports of “ineffective indirect fire in the vicinity of the base.”

The area in Anbar Province has long been a hot zone of fighting as ISIS looks to hold and expand its self-declared caliphate in Iraq and Syria. In January, the Pentagon first confirmed that U.S. troops at the Al Asad base had been coming under regular mortar fire.

To date, those attacks have been described as ineffective. A senior U.S. official told Fox News the base receives “low-scale” indirect fire from time to time.

“We continue to support efforts by Iraqi Security Forces, working in conjunction with tribal fighters, directed against ISIL in the province,” the DOD spokeswoman said Thursday.

Another Pentagon spokesman, Col. Steven Warren, said the U.S. troops were about 2 miles away, in a different section of the base.

According to The Times, American intelligence officials estimate that the terror group’s fighters have reached as many as 31,000 in Syria and Iraq.

U.S. unmanned surveillance aircraft and Army Apache attack helicopters were sent to the scene from Baghdad, but the attack was over before they arrived, so they did not engage in fighting, Warren said.

There are currently nearly 2,600 U.S. forces in Iraq. Of those, about 450 are training Iraqi troops at three bases across the country, including al-Asad.

Forces from other coalition countries conduct the training at the fourth site, in the northern city of Irbil.

The development comes as the U.S.-led coalition continues to launch airstrikes against ISIS, with Jordan taking on a greater role following the brutal execution of a captured Jordanian pilot at ISIS’ hands.

Fox News’ Lucas Tomlinson contributed to this report.

The Associated Press contributed to this report.