The State Seismological Center, affiliated to the Geophysics Institute of Tehran University, registered the quake at 03:15 hours local time (2245 GMT Sunday).
The epicenter of the quake was reported at 56.56 degrees longitude and 32.73 degrees latitude.
There has been no report on probable human or material losses.
Iran sits astride several major fault-lines on the earth and is prone to frequent earthquakes which in many cases were devastating.
The deadliest quake in the country occurred in June 1990 measuring 7.7 on the Richter scale in northern provinces of Gilan and Zanjan region. Some 37,000 people were killed and more than 100,000 injured by that earthquake.