Two mortars landed inside Iraq's Balad air base on Thursday, two Iraqi military sources said.
No casualties have been reported in the mortar attack against the air base, said the sources.
Balad base hosts U.S. forces and contractors and is located about 80 kilometres (50 miles) north of Baghdad.
On Tuesday, five rockets landed on Ain Al-Asad air base, which hosts U.S. forces in Anbar province in western Iraq without causing any casualties.
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