Iran's state TV says that an Iranian Phantom fighter jet has crashed close to the Pakistan border, killing two pilots.

It reported that the crash took place on Tuesday morning some 45 miles west of Konarak Air Base, around 900 miles southeast of the Iranian capital, Tehran.

The report said that the cause of the crash was unknown but investigations were ongoing. The pilots were on a training assignment.

Iran's Air Force purchased the U.S.-manufactured Phantom warplanes before the 1979 Islamic Revolution. It also has Iranian and Russian-made fighters in service.

Several warplane crashes have taken place in Iran in recent years. Most recently, in July 2014, an F-4 fighter jet crashed in the south of the country, killing two pilots.