The US military struck an Iranian position near the Strait of Hormuz from which drones were being operated, a US official said.
The military also shot down four drones that posed a threat to the United States, the official said, adding that the targeted position in the southern Iranian port city of Bandar Abbas had been preparing to launch a fifth drone.
"These actions were measured, purely defensive, and intended to maintain the ceasefire," the official added.
The US account of the incident could not immediately be independently verified.
A US official quoted by CBS News said the ceasefire that has been in place since early April remained intact despite the incident. Only days earlier, however, the warring sides had exchanged attacks near the Strait of Hormuz.
Iranian media had earlier reported explosions in southern Iran. Iran's Fars news agency said three explosions were heard east of Bandar Abbas early on Thursday, adding that air defences had been activated.
Bandar Abbas, the capital of Hormozgan province, is one of Iran's most important military hubs in the Gulf region and along the Strait of Hormuz.
