According to the Seismological Center of the Geophysics Institute of Tehran University, the tremor occurred at 02:52 hours local time (11:22 GMT) at the depth of 13 km underground.
The epicenter of the quake was 36 kms from Qasr-e Shirin, 62 kms from Sarpolzahab and 66 kms from Ozgoleh city of Kermanshah Province.
No report on the possible casualties or damage to properties has so far been released.
Iran sits on major fault lines and is prone to near-daily earthquakes.
In 2003, a 6.6-magnitude quake flattened the historic city of Bam, killing 26,000 people.
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