An Iranian soldier has killed three colleagues and wounded 12 at a military air base in Tehran, the semi-official Mehr news agency reported.
One of the victims was an officer and the others were regular soldiers. The attacker was killed in a shoot-out with other soldiers.
All of the injured soldiers were taken to an Air Force hospital in the south east of the city.
The shooting is the latest to strike Iran.
In July, a soldier opened fire on his comrades, killing three and wounding six at a military base in the town of Abyek, 62 miles west of Tehran. The assailant reportedly shot himself in the incident but survived and was taken to a nearby hospital.
In September, a soldier killed himself after shooting dead three of his comrades in the south of the country.
Military service of up to 24 months is mandatory for men aged 19 and above in Iran.