The incident occurred on Saturday on the road from Kordkuy County to the provincial capital city of Gorgan, reports Xinhua, quoting the official news agency IRNA.

The sole victim of the incident died after having been transferred to the hospital, IRNA quoted Mohammad-Javad Moqassemi, head of the emergency medical services of Golestan University of Medical Sciences, as saying.

All the 21 people injured in the accident had been transferred to medical centres and were in good condition, said Moqassemi.

According to local media reports, the bus overturned after deviating from its route and hitting the guardrail and the pier of a pedestrian overpass, causing heavy traffic on the road.

It added that there were 20 passengers aboard the bus, along with the driver and his assistants, as they made their way to Tehran.