The Seismological center of Yazd province affiliated to the Geophysics Institute of Tehran University registered the quake at 00:38 hours local time (2008 GMT Thursday night).
The epicenter of the quake was located in an area 56.2 degrees in longitude and 32.9 degrees in latitude.
There are yet no reports on the number of possible casualties or damage to properties by the quake.
Iran sits astride several major faults in the earth's crust, and is prone to frequent earthquakes, many of which have been devastating.
The worst in recent times hit Bam in southeastern Kerman province in December 2003, killing 31,000 people - about a quarter of its population - and destroying the city's ancient mud-built citadel.
The deadliest quake in the country was in June 1990 and measured 7.7 on the Richter scale. About 37,000 people were killed and more than 100,000 injured in the northwestern provinces of Gilan and Zanjan. It devastated 27 towns and about 1,870 villages.