The quake hit the city of Sisakht at 08:38 local time (04:08 GMT), making people rush out to the streets, the IRNA news agency reported, citing the Seismological Center of the Geophysics Institute of Tehran University.
The earthquake's epicenter was located at a depth of 8 kilometers underground. There is no information on the damage to infrastructure yet.
According to the Tasnim news agency, the number of victims has increased to 105. Earlier, representative of the Iranian emergency situations organization, Mujtaba Khalidi, had informed that there were 76 injured.
At least 32 of those injured have been taken to hospital, while 65 others received outpatient treatment, the Tasnim news agency reported.
Iran is located on major fault lines and is prone to near-daily earthquakes.
A 7.2-magnitude earthquake in November hit the Kurdish town of Sarpol-e-Zahab and killed 600 people.
In 2003, a 6.6-magnitude earthquake razed the historic city of Bam to the ground, killing 26,000 people.