Bagheri, quoted by the official news agency IRNA, described the site as a "safe operational base for strategic drones".
"We never underestimate threats, we never assume the enemy is asleep, and we are constantly alert and vigilant," he added.
Mousavi told state television the base was located "several hundred metres (yards) underground", without giving further details.
State TV said the flagship of the fleet was the "Kaman-22", a drone equipped with missiles and able to fly at least 2,000 kilometres (1,245 miles).