IS fighters had surrounded the town of about 17,000 ethnic Turkmen Shiites, leaving the residents without power, food, water and other supplies.
The Sunni militants, also known as ISIS or ISIL, had taken control of strategic locations throughout Iraq and Syria, including several villages surrounding Amerli.
The United States conducted airstrikes against IS-controlled locations near the northern Iraqi town of Amerli and dropped aid for residents after nightfall Saturday, Pentagon press secretary Rear Adm. John Kirby said. As part of the offensive, the Iraqi military entered the town to evacuate vulnerable residents.
Residents celebrated the broken siege, waving Iraqi flags and firing gunshots into the air, retired Gen. Khaled al-Amerli told CNN.
"Today is a day of victory for Iraq and the resilient people of Amerli," he said.
Australia, France and Britain also participated in the humanitarian air drop.