SINJAR, Iraq -- Kurdish Iraqi fighters, backed by the U.S.-led air campaign, launched an assault Thursday aiming to retake the strategic town of Sinjar, which the Islamic State group overran last year in an onslaught that caused the flight of tens of thousands of Yazidis and first prompted the U.S. to launch airstrikes against the militants.
A statement from the Kurdish Regional Security Council said some 7,500 peshmerga fighters were closing in on the mountain town from three fronts in an effort to take control of the town and cut off a strategic supply line used by the Islamic State militants. The statement also said the operation, dubbed Operation Free Sinjar, is aimed at establishing "a significant buffer zone to protect the city and its inhabitants from incoming artillery."
Peshmerga fighters and the militants exchanged heavy gunfire in the early hours Thursday as Kurdish fighters began their approach amid heavy aerial bombardment. An Associated Press team saw a small American unit at the top of a hill along the front line calling in and confirming airstrikes.
Hours into the operation, the security council said Kurdish forces had successfully secured the village of Gabarra and controlled a section Highway 47, of one of IS's most active supply lines, and they captured the villages of Gretishore and Fadhellya on the eastern front.
"(Peshmerga) troops are holding their position, waiting for reinforcements and more airstrikes so they can then move into the center of the town. Airstrikes have been very important to the operation getting to the point where it is now," said Maj. Gen. Seme Busal, commander of one of the front lines. He said peshmerga fighters were in a similar position on the other front lines, waiting for reinforcements or more airstrikes in order to push into the more urban areas of Sinjar.
Sinjar was captured by the Islamic State group in August 2014 shortly after the extremists seized Iraq's second-largest city, Mosul, and blitzed across northern Iraq.
The major objective of the offensive is to completely cut off Highway 47, which passes by Sinjar and indirectly links the militants' two biggest strongholds -- Raqqa in Syria and Mosul in northern Iraq -- as a route for goods, weapons and fighters. Coalition-backed Kurdish fighters on both sides of the border are now working to retake parts of that corridor.
"If you take out this major road, that is going to slow down the movement of (IS's quick reaction force) elements," Capt. Chance McCraw, a military intelligence officer with the U.S. coalition, told journalists Wednesday. "If they're trying to move from Raqqa over to Mosul, they're going to have to take these back roads and go through the desert, and it's going take hours, maybe days longer to get across."
Kurdish officials said clouds of smoke above Sinjar on Thursday were making it more difficult for coalition planes to carry out airstrikes on the city as thousands of Peshmerga fighters move into the town from the east and west and massed at the edges.
Capt. Ramazan Sanaan, commander of a base atop a mountain overlooking the town said he and his men were waiting for peshmerga units on the eastern and western approaches to the town to cut off the main supply road in and out of Sinjar before they move in.
"Actually it's going very slow," he said. The progress was hampered by explosives and roadside bombs, a favored weapon of the IS group in Iraq.
Warplanes in the U.S.-led coalition have been striking around Sinjar ahead of the offensive and strikes grew more intense at dawn Thursday as bombs pounded targets outside the town. But Sinjar, located at the foot of Sinjar Mountain about 30 miles (50 kilometers) from the Syrian border, is not an easy target. One attempt by the Kurds to retake it stalled in December. The militants have been reinforcing their ranks in Sinjar recently in expectation of an assault, since "this operation has been building for a while," Maj. Michael Filanowski, operations officer for the U.S.-led coalition, said Wednesday, though he could not give specifics on the size of the IS forces there.
"On the radio we hear (IS) calling for reinforcements from Syria," Rebwar Gharib, a deputy sergeant on the central front line in Sinjar, said Thursday.
In the Sinjar area, the Islamic State group inflicted a wave of terror against the minority Yazidi community, members of an ancient religion whom the Islamic State group views as heretics and accuses of worshipping the devil. An untold number were killed in the August 2014 assault, and hundreds of men and women were kidnapped -- the women enslaved and given to militants across the group's territory in Iraq and Syria, many of the men believed killed, others forced to convert.
Tens of thousands of Yazidis fled into the mountains, where the militants surrounded them, leaving them trapped and exposed in the blazing heat. The crisis prompted the U.S. to launch air drops of aid to the stranded, and then on August 8, it launched the first round of airstrikes in what would mark the beginning of a broader coalition effort to battle the militant group in Iraq and Syria.
Some of those stranded on Mount Sinjar were rescued by Syrian Kurdish fighters, who cleared a path for the Yazidis to descend from the mountain, cross into Syria, then cross back into northern Iraq's Kurdish autonomous zone. Then, in December, Kurdish fighters in northwestern Iraq managed to drive the militants out of areas on the other side of the mountain, opening a corridor that helped many of the remaining displaced Sinjaris to escape. Those Kurdish fighters then tried to advance into Sinjar town itself but were fought off by the militants.
Various Kurdish militias on the town's edge have been fighting guerrilla battles for months with IS in Sinjar, leaving much of the picturesque town of ancient, narrow streets lined with modest stone homes damaged or destroyed. The factions include the Turkey-based Kurdish Workers' Party (PKK), the Syria-based People's Protection Units (YPG) and Yazidi-led forces billing themselves as the Sinjar Resistance. Iraqi Kurdish fighters have also held positions further outside the town.
Associated Press writer Vivian Salama in Baghdad contributed to this report.