Iranian media reported on July 17 that a soldier opened fire on his comrades, killing three and injuring six others before killing himself.
The reports from Mehr news agency and Iranian television said the incident took place when soldiers were resting at a military base in the town of Abyek, northwest of Tehran.
The attack occurred after higher officers opposed the attacker's request for a transfer to his hometown, reports said. None of the soldiers were identified.
"The reason for this heartbreaking incident is being examined and we can’t speak about it now before investigating," said Ali Reza Rahmani, Abyek's governor.
In September, a soldier killed himself after shooting to death three of his comrades.
Military service of up to 24 months is mandatory for men aged 19 and above in Iran.