A drone attacked Erbil airport in northern Iraq with explosives on Tuesday, aimed at the US base on the airport grounds, Kurdish security sources said.
Sirens were blaring from the US consulate in the city, the capital of Iraqi Kurdistan, 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.
The attack comes one day after rockets and a drone targeted Ain al-Asad air base, which houses US troops and the US embassy in Baghdad, on Monday.
In April, a drone dropped explosives near the US forces stationed at Erbil airport. It was then the first known attack carried out by an unmanned aerial drone against US forces in Erbil, amid a steady stream of rocket attacks on bases hosting US forces and the embassy in Baghdad that Washington blames on Iran-backed militias.