Iraqi security forces, along with Shiite militiamen, broke a nearly two-month siege by Islamic State militants on the northern Shiite Turkmen town of Amirli, Iraqi officials said on Sunday.

Army spokesman Lt. Gen. Qassim al-Moussawi said the operation started at dawn Sunday and the forces entered the town shortly after midday, The Associated Press reported.

Speaking live on state TV, al-Moussawi said the forces suffered "some casualities," but did not give a specific number. He said fighting was "still ongoing to clear the surrounding villages."

Breaking the siege was a "big achievement and an important victory" he said, for all involved: the Iraqi army, elite troops, Kurdish fighters and Shiite militias.

However, U.S. officials would not confirm reports that security forces had broken the siege and Pentagon sources told Fox News to expect more U.S. airstrikes in the Amerli area throughout Sunday.

About 15,000 Shiite Turkmens had been stranded in the farming community, some 105 north of Baghdad. Instead of fleeing in the face of the Islamic State drive across northern Iraq, the Shiite Turkmens have stayed and fortified their town with trenches and armed positions.

Iraqi troops began the push to retake the town from ISIS on Saturday. Its water and electricity have been cut off since June and surrounded by militants since mid-July.

Some residents have said that the Iraqi military's efforts to fly in food, water and other aid have not been enough amid oppressive heat, lack of electrical power -- the town's power station was destroyed weeks ago -- and shelling from the militants.

The U.S. had been watching the area closely in case a slaughter of the Turkmen appeared imminent and air support was needed, said Michael Knights, who studies Iraq and the Persian Gulf as a fellow of The Washington Institute. U.S. airstrikes will hasten the success of the relief effort on the ground, he said.

About half of the town's population is age 15 and under while many others are elderly, sick or wounded, Knights said.

"They are remarkably vulnerable, and ISIS is determined to kill as many of these people as possible," Knights said, referring to an acronym for the Islamic State group. "As the Nazis felt about the Jews, so ISIS feels about the Shia Muslims."

The Turkmen are Iraq's third largest ethnic group after Arabs and Kurds. They make up about 4 percent of Iraq's population. Iraqi forces were airlifted into the area on Saturday

"We thank God for this victory over terrorists," al-Bayati told The Associated Press by phone from the outskirts of Amirli. "The people of Amirli are very happy to see that their ordeal is over and that the terrorists are being defeated by Iraqi forces. It is a great day in our life."

State TV stopped regular programs and started airing patriotic songs following the victory announcement, praising the country's security forces. They have been fighting the militants for weeks without achieving significant progress on the ground.

On Saturday, the U.S. conducted airstrikes against the Sunni militants and air-dropped humanitarian aid to residents. Aircraft from Australia, France and Britain joined the U.S. in the aid drop, which came after a request from the Iraqi government. The U.S. Central Command said another airstrike on Sunday damaged a tank used by Islamic State fighters.

The Pentagon's press secretary, Rear Adm. John Kirby, said military operations would be limited in scope and duration as needed to address the humanitarian crisis in Amirli and protect the civilians trapped in the town.

The Islamic State extremist group has seized cities, towns and vast tracts of land in northeastern Syria and northern and western Iraq. It views Shiites as apostates and has carried out a number of massacres and beheadings -- often posting grisly videos and photos of the atrocities online.

The Associated Press and Fox News’ Jennifer Griffin contributed to this report.