The quake occurred just after 5 a.m. local time, 44 kilometers (27 miles) southeast of the city of Borazjan in Bushehr province, at a depth of 38.3 kilometers (23.7 miles), according to the US Geological Survey (USGS).
The Bushehr nuclear plant is located on the Iranian coastline to the southwest of Borazjan, not far from the epicenter of the earthquake.
So far there has been no official word on whether or not the plant was damaged by the earthquake.
History of deadly quakes
The deadliest quake this century occurred in 2003 when a magnitude 6.6 earthquake struck the southeastern city of Bam, killing some 26,000 people.