Several blasts hit a position held by Iraqi Shiite paramilitaries next to Balad air base north of Baghdad on Tuesday, an Iraqi military official and a source in a paramilitary group said.
Balad base hosts US forces and contractors and is located about 80 km (50 miles) north of Baghdad. An Iraqi Shiite militia group, which is backed by Iran (IMIS), is stationed nearby.
The military official said the intended target of the blasts was the militia's position near the base. The paramilitary source said his group's weapons depot was specifically targeted by an aerial bombardment.
The US-led coalition could not immediately be reached for comment. There were no immediate reports of casualties.
Witnesses said the explosions caused stored rockets to fly into nearby orchards and into Balad base itself.