The explosion in the Eastern Alborz Coal Mine in Tazreh happened at 19:30 local time (16:00 GMT) on Sunday due to gas accumulation, which trapped the six miners at a depth of 700 meters.
A number of workers also suffered from gas poisoning.
Rescue teams were dispatched to the scene immediately after the collapse of the mine located north of Damghan in Semnan Province.
Tazareh coal mine has a history of similar deadly incidents. In May 2021, a blast claimed the lives of two miners.
The accidents are common in Iran, where much of the infrastructure is outdated, partly due to international sanctions that have blocked the importing of new equipment.