Militants apparently perched on nearby mountains fired three rockets on the gathering in Kalaya town of tribal Orakzai district, senior administration official Sahabzada Anis said, giving the toll.
One hit the gathering but struck before the arrival of Khyber Pakhtunkhwa governor Masood Kausar, he told AFP.
A second rocket landed near a helipad and a third fell in surrounding fields, he said.
Copyright AFP (Agence France-Presse), 2011