In November, a 7.2 magnitude quake struck the same region, killing more than 530 people and injuring thousands in Iran alone. The quake had left around 328 people dead.
At least 600 Iranians died in a 7.3-magnitude natural disaster that hit the Kermanshah province on November 12 previous year.
AFP correspondents said the quakes were also felt across Iraq and in Iraqi Kurdistan bordering Iran. Earthquakes at magnitude 5 can cause considerable damage. "If there was a stressed fault that's ready to move, they happen like that until the stresses are relieved, so it's not too unusual".
The epicenter of the quake was 31 km west of Kerinshah at a depth of 10 km. Many people are still living in temporary homes and tents. Sarpol-e Zahab suffered half of the temblor's casualties.
The region, largely rebuilt in recent decades after Iran and Iraq's ruinous 1980s war, saw many buildings collapse or sustain major damage in the November quake.
Magnitude Quake Strikes Western Iran
There were no immediate reports of injuries or damage.
The official IRNA news agency says the temblor rocked the village of Hojedk, located about 700 kilometers, or 400 miles, south of Tehran early on Thursday.
Iran is one of the most seismically active countries in the world, being crossed by several major fault lines that cover at least 90% of the country.
A magnitude 6.6 natural disaster flattened the historic city of Bam in south Iran and killed 26,000 people in 2003.
Late Thursday afternoon, another 4.8 magnitude natural disaster struck in Kerman, according to the USGS.