The unmanned aircraft targeted a suspected hideout of militants in Datakhel area of the district.
A security official said that four missiles were fired from the drone which destroyed a compound. "Initial reports show that 18 militants were killed.
The identity of those killed is not known as yet," he said. It was second drone attack within week, after seven militants were killed in a similar strike in the same area on July 10.
Pakistan first said that it was not aware of the attack but later condemned it, showing its tight policy position vis-a-vis drone campaign, as they target the same rebel Pakistan army is trying to wipe out. The country terms these attacks as violation of its sovereignty.