The earthquake occurred at 3:34 a.m. local time at a depth of 16 kilometers in Sankhast, 70 km southwest of the capital city of Bojnourd, according to the Seismological Center of the Geophysics Institute of Tehran University.
No fatalities have so far been reported in the aftermath of the quake, IRNA reported.
Twelve other quakes measuring 2.6-5.4 on the Richter scale shook the area within 6 hours.
Some 11 rescue and relief teams and a helicopter have been dispatched to the quake-hit areas for assessment, and in addition, relief items have been sent to the scene.
North Khorasan province is located on active and important faults, which sometimes cause destructive earthquakes with their movements.
The most important fault of North Khorasan is Esfarayen fault, which is about 170 km long, Baghan-Garmab fault is also a fault with a length of 55 to 50 km.
According to the statistics, 13 earthquakes with a magnitude of more than 5.5 occurred in North Khorasan over the current century.
The Iranian plateau is located in a very seismically active region of the world and is known not only for its major catastrophic earthquakes but also for the disasters relating to natural hazards, especially earthquakes.
About 2 percent of the earthquakes of the world occur in Iran but more than 6 percent of the victims of the world earthquakes during the 20th century are reported from Iranian earthquakes. This shows the high level of vulnerability in Iran, according to Mehdi Zare, a professor of engineering seismology.
Most recently, a magnitude 5.9 earthquake jolted southwestern Bushehr province on April 18, leaving 5 injured.