BARTELLA, Iraq (AP) — In a significant intensification of the battle for Mosul, elite Iraqi special forces joined the fight Thursday, unleashing a pre-dawn assault on an Islamic State-held town east of the besieged city. The U.S. military announced the first American death since the operation began.

Central Command said the U.S. soldier died Thursday from wounds sustained in a roadside bomb explosion in northern Iraq, but did not say if the soldier was part of the Mosul campaign. More than 100 U.S. special operations forces are embedded with Iraqi units in the offensive, and hundreds more are playing a support role in staging bases.

As Iraq's special forces advanced on the town of Bartella, nine miles (15 kilometers) from Mosul's outskirts, they faced a familiar foe — trucks packed with explosives and driven by suicide bombers.

The militants' signature battlefield tactic, the weapons offered a glimpse at what Iraqi forces can expect as they approach the extremists' biggest urban bastion.

The pre-dawn assault was part of a multi-pronged operation on eastern approaches to Mosul, Iraq's second-largest city. Attack helicopters strafed militant positions as they advanced amid a hail of gunfire.

The U.S.-trained special forces , officially known as the Counter Terrorism Service, are widely seen as Iraq's most professional and least sectarian fighters, and have served as the shock troops in previous campaigns against IS. They are expected to lead the charge into Mosul.

IS militants unleashed at least nine suicide car and truck bombs against the advancing troops, eight of which were destroyed before reaching their targets, while the ninth struck an armored Humvee, Lt. Col Muntadhar al-Shimmari told The Associated Press.

He did not give a casualty figure, but another officer said five Iraqi soldiers were wounded. The officer spoke on condition of anonymity because he was not authorized to release information.

"After we break them in Bartella, everywhere else, they will crumble," said Maj. Gen. Fadhil Barwari. He said IS had few defenses in the town, which was almost completely empty of civilians. "They just left some snipers and suicide car bombs," he said.

Meanwhile, Iraqi Kurdish forces, known as peshmerga, announced a simultaneous attack, with peshmerga fighters deployed on mountains northeast of Mosul descending from their positions and charging toward the front line.

Under cover of mortar and gunfire, the Kurdish troops used bulldozers and other heavy equipment to fill trenches dug by the militants as part of their defense of the IS-held village of Barima, then advanced with their armored vehicles toward the extremists' positions.

Military operations also appeared to be underway in the town of Bashiqa, northeast of Mosul, where thick smoke could be seen billowing up. A day earlier, Bashiqa was pounded by airstrikes and mortar fire from peshmerga positions high above.

Lt. Gen. Talib Shaghati told a news conference late Thursday that the special forces had succeeded in retaking Bartella. But Iraqi forces were still facing stiff resistance inside the town shortly before he spoke, and past advances against IS elsewhere in Iraq have often proved fleeting.

Soldiers stationed a few miles (kilometers) from Bartella said they watched as some 20 car bombs exploded in the town over the course of the day, each one sending a plume of smoke into the air. By late afternoon the skies over Bartella were black.

IS has used the tactic in past battles to wreak havoc among front line troops, but Iraqi forces have become better at stopping the suicide attackers.

"We destroyed the bombs with tanks," Sgt. Maj. Qusay Rashid said. "They are sending all these car bombs now because we're at the beginning of this huge battle. They are trying to put up their best defense."

After Bartella, Iraqi forces advancing toward Mosul will begin to hit villages and suburbs where civilians still live, a factor that will further complicate military operations that rely heavily on artillery and airstrikes to clear territory.

Mosul is home to more than a million people, and rights groups fear a potential humanitarian crisis.

Meanwhile, Prime Minister Haider Al-Abadi said Mosul may fall sooner than expected. The campaign to retake the city, which began Monday, had been expected to last weeks, if not months.

Speaking by video transmission to a conference in Paris focused on post-liberation planning for Mosul, the Iraqi leader said the Iraqi "forces are currently pushing forward ... more quickly than we thought, and more quickly certainly than we established in our plan of campaign."

The Islamic State group captured Mosul and the surrounding area during a lightning advance across northern Iraq in the summer of 2014, and IS leader Abu Bakr al-Baghdadi announced the formation of a self-styled caliphate from the pulpit of a Mosul mosque.

Iraqi forces crumbled that summer, beating a humiliating retreat and leaving weapons and vehicles behind. But the special forces held together and fought back, and since then they have played a central role in retaking cities and towns from the extremist group.

The force was created by U.S. Special Forces shortly after the 2003 invasion to hunt down top insurgents and stage commando raids, but its mandate has since expanded. Its members include Shiites, Sunnis and Kurds, and its human rights record is better than other forces taking part in the operation.

Mosul is a Sunni majority town, and many fear the involvement of state-sanctioned Shiite militias in the operation could stoke sectarian tensions. The Shiite militias have said they will not enter the city itself.

But even among the special forces there are traces of sectarian fervor. Many of the black Humvees that rode into battle in Bartella were decked with Shiite religious banners in addition to Iraqi flags.

Ali Saad, a 26-year-old special forces soldier, said Kurdish forces had asked them to take down the religious banners, but they refused.

"They asked if we were militias. We said we're not militias, we are Iraqi forces, and these are our beliefs," he said.

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Associated Press writers Joseph Krauss and Sinan Salaheddin in Baghdad, Adam Schreck in Irbil, Iraq, and Balint Szlanko on Nawaran mountain contributed to this report.