Sirens were blaring from the U.S. consulate in the city, the capital of the region, the sources said.
Flights were suspended following the attacks, they said.
In a statement, the Pentagon said it was aware of reports about a drone attack, but initial information did not indicate structural damage, or injuries or casualties.
Another spokesman for the U.S. military, citing initial information, said one drone had "impacted" near Erbil, but that there were no injuries or any damage, Reuters reported.
The attack comes a day after rockets and a drone targeted Ain al-Asad air base, which houses U.S. troops, and the U.S. Embassy in Baghdad.
In April, a drone dropped explosives near the U.S. forces stationed at Erbil airport. That was the first known attack carried out by an unmanned aerial drone against U.S. forces in Erbil, amid a steady stream of rocket attacks on bases hosting U.S. forces and the embassy in Baghdad that Washington blames on some Iraqi militias.
Reporter's code: 50101