IRBIL, Iraq — An attempt by Islamic State to evacuate hundreds of fighters from western Syria to the Iraqi border has instead left them sitting ducks for aerial attacks by the U.S.-led coalition on the convoy.

“We were able to exploit it and take advantage,” Army Col. Ryan S. Dillon, a coalition spokesman, said of the ISIS maneuver Thursday morning as 11 buses full of ISIS fighters and civilians remained stranded in the Syrian desert.

U.S. warplanes continue to pick off militants who stray too far from the protection of the convoy’s women and children, officials said. Strikes have also destroyed militant vehicles coming to the area from ISIS-held territory.

“Like moths to the flame,” more than 40 vehicles have come to try to aid the convoy, including armored technical vehicles and a tank disguised as a truck, Dillon said. “We were able to continue to just observe and pick them off one at a time.”

More than 300 ISIS fighters and about as many women and children had set off about 10 days ago from an enclave on the Lebanon-Syria border after surrendering and brokering a deal with Lebanon’s Hezbollah militant group for safe passage through Syrian government-held territory. They rode on 17 buses bound for extremist-held areas farther east.

But the U.S.-led coalition, which was not a party to the agreement, quickly scrambled to block their progress. Airstrikes cratered the roadway, disabled a bridge and stranded the convoy in no man’s land between Syrian- and ISIS-held territory on the border with Iraq. This forced six buses to turn back toward the city of Palmyra — and the protection of the Syrian army and Hezbollah.

In recent days, a group of nearly a dozen militants on an apparent scouting mission were targeted after they ventured far enough away from the group of 11 buses, ensuring that civilians would not be harmed in a strike, Dillon said. In all, more than 85 militants have been killed since the convoy was halted 10 days ago, which has saved the coalition the effort of hunting them down, he said.

U.S. officials have disputed claims by Syrian opposition activists that dozens of the ISIS fighters and their families had still managed to cross into ISIS-held areas using civilian vehicles. The convoy “has not ... and will not reach Iraq,” Brett McGurk, special presidential envoy for the coalition, said Wednesday on Twitter.

The coalition watched the buses that turned back until they were near Palmyra and has constantly monitored the others marooned on the road to the Iraqi frontier, Dillon said.

The coalition has promised to prevent the experienced fighters from linking up with extremists to the east but is continuing to allow supplies of food and water to reach the convoy from the Syrian government side, he said. A delivery on Tuesday night ended with the fighters showing apparent signs of frustration at being pinned down as they attacked each other.

“You could clearly tell they were going to fisticuffs,” Dillon said.

garland.chad@stripes.com

Twitter: @chadgarland