The pilots of two-seater jet were killed as a result of the abnormal activation of the ejection seats, according to the IRIB news agency.
The incident took place on Tuesday morning at the Dezful air force base in the southwestern province of Khuzestan.
In 2018, another F-5 fighter jet had crashed in southern Iran, killing its pilot. The co-pilot managed to survive. The cause of the incident wasn’t revealed.
Iran bought its F-5 fighters from the United States before the 1979 Islamic Revolution.
The Northrop F-5 is a family of supersonic fighter jets, initially designed in the late 1950s by Northrop Corporation. In some countries, it remains in service to support training exercises.
Earlier this month, a Swiss Air Force F-5 jet crashed in the central canton of Obwalden. The pilot of the F-5 Tiger successfully ejected from the cockpit and survived the crash.