Gov. Ahmadu Fintiri of Adamawa is Chairman of the Electoral Committee.
According to NAN, the voting process had ended and the sorting of votes was ongoing when the suspected gunmen stormed the venue of the primary and started shooting.
A further report had it that votes in eight out of the 10 ballot boxes had already been counted and sorted out before the invasion of the gunmen.
Aspirants, delegates and others scampered for safety while the number of casualties is yet to be ascertained.
The winner of the PDP governorship primary will contest against the incumbent governor of the state, Yahaya Bello, who won the All Progressives Congress (APC) ticket last week and other aspirants from other parties.