The report said the quake hit yesterday evening in the district of Goharan, about 1,200 kilometers (750 miles) southeast of the capital Tehran.
It says many buildings were damaged and that rescue workers were on the scene.
The quake affected cellular phone coverage in the region with a population of 15,000 in nearly 80 villages. No casualties are reported so far.
Iran sits on a series of seismic fault lines and experiences one slight quake a day on average.
In 2003, some 26,000 people were killed by a magnitude 6.6 quake that flattened the historic southeastern Iranian city of Bam.