An Iranian serviceman shot dead three fellow soldiers at a barracks on Monday and wounded six others before killing himself, the Mehr news agency reported.
The shooting took place in the town of Abyek, some 40 km (25 miles) northwest of Tehran, Mehr said.
"The reason for this heartbreaking incident is being examined and we can't speak about it now before investigating," said Ali Reza Rahmani, the town's governor.
Such incidents are rare in the Iranian military.
