Four young Saudi pilgrims have died in Iran as a result of an accidental mass poisoning in their hotel, according to reports.

The official IRNA new agency said the victims included a 14-year-old girl and three young boys, all age 3.

Another 28 Saudi religious pilgrims were taken to hospital over exposure to the poison, which is commonly used to kill insects and rats.

The incident took place in the north-eastern Iranian city of Mashhad, which is home to a major Shiite Muslim Shrine.

The city is visited by nearly two million foreign pilgrims per year, coming from Saudi Arabia, Iraq, Bahrain, Azerbaijan and the Indian subcontinent.

Authorities say they are investigating the incident.