(CNN) Coalition airstrikes targeted two ISIS convoys leaving Falluja over two days, destroying about 175 vehicles carrying militants out of the city, the spokesman for the U.S. coalition said Thursday.

Col. Chris Garver said Iraqi security forces destroyed other vehicles.

The Iraqi military provided different numbers, saying coalition and Iraqi forces destroyed a total of 750 ISIS vehicles in the two convoys and killed hundreds of ISIS militants.

One of the convoys consisted of 700 vehicles, said the commander of the Iraqi Air Force, Lt. Gen. Hamed al-Maliki.

Defense Minister Khalid al-Obeidi said 688 ISIS vehicles were destroyed and 440 ISIS militants killed

Garver didn't say how many militants were killed. A U.S. official said the destroyed vehicles could have carried as many as 250 ISIS fighters.

Garver said a large group of vehicles was detected gathering in neighborhoods southwest of Falluja, west of the Tofaha Bridge, on Tuesday night. Iraqi security forces on the ground positively identified the convoy as belonging to ISIS, he said.

"Iraqi air force and coalition airstrikes attacked the convoy throughout the night and into Wednesday morning," Garver said. "We estimate coalition strikes destroyed approximately 55 Daesh vehicles and we know the Iraqi security forces destroyed more." Daesh is another term for ISIS.

On Wednesday, a second group of ISIS vehicles and fighters formed east of Ramadi, in the Albu Bali neighborhood, Garver said.

"When strikes from both Iraqi and coalition air hit the convoy, the Daesh fighters abandoned their vehicles and fled on foot," he said. "We estimate coalition strikes destroyed approximately 120 Daesh vehicles. Again, we know the Iraqi security forces destroyed more."

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The operation required American aircraft because there were a lot of civilians in the area, a U.S. official said.

The airstrikes come days after the Iraqi military announced that its troops had seized Falluja from ISIS.

The city was liberated Sunday after the military recaptured the last neighborhood in Falluja, said Lt. Gen. Abdul Wahab al-Saadi, commander of the liberation of the city.

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Humanitarian group dodges airstrike, ISIS

The airstrikes apparently came close to hitting members of a humanitarian group.

In a blog on the Preemptive Love Coalition's website , Matthew Willingham wrote that two trucks carrying food to Falluja residents who'd fled the fighting became stuck in a rut. Part of the group stayed with the vehicles and the others headed to Baghdad.

ISIS forces soon swept across the southern Falluja corridor, with a convoy of 450 ISIS vehicles passing by the stuck trucks, Willingham wrote.

"The team guarding the trucks climbed down into a nearby ditch and pulled sand over themselves as ISIS vehicles began passing on the road. Our team leader counted about 80 vehicles with fighters bearing small arms. In the middle of the night, he messaged us: 'They are right here next to me... ' Thankfully, the vehicles kept moving," Willingham wrote.

The group that headed to Baghdad was held up at a military checkpoint near Amiriyat al-Falluja, several miles southeast of Falluja, and slept that night on a concrete slab. In the morning they were stretching their legs when the missiles starting hitting the ground, Willingham wrote.

"Everyone dove for cover. An airstrike had hit just a few feet from our convoy, right where the team had been before taking their walk. One of the men was only a few meters from the blast," he wrote.

They ran toward the checkpoint but soldiers aimed their guns and told them to stay back, he write. Other missiles hit nearby. Hours later, a local tribal leader helped move the truck and got the other team through the checkpoint.

"U.S. forces acknowledged they were conducting airstrikes on ISIS convoys in the area, though they stopped short of acknowledging strikes at the exact coordinates we gave them," Willingham wrote. "But now, the team is back in Baghdad, where they are safely resting."

Hundreds of militants killed

Iraqi forces killed more than 1,800 ISIS militants during the operations to recapture the city of Falluja and villages surrounding it, al-Saadi said Sunday. CNN cannot independently verify all fighting in every area of Falluja has ended.

ISIS appears to be on the defensive across the Middle East -- from its self-declared capital of Raqqa in Syria to Falluja, a strategically important city just 65 kilometers (40 miles) from the Iraqi capital, Baghdad.

In a symbolic victory, Iraqi police raised the national flag over the Falluja mayor's office.

U.S.-backed offensive

The move came nearly four weeks after the start of a U.S.-backed offensive to liberate the city, which was the last major ISIS foothold in Iraq's Anbar province.

Fierce fighting has taken place street by street, and bombs remain a concern as ISIS fighters flee the city.

Many houses are booby-trapped, forcing Iraqi forces to move slowly and methodically to clear improvised explosive devices.

Despite the complete recapture of Falluja, aid groups stressed that safety is still a concern and urged displaced families not to return home.