Iranian state TV says an air force Sukhoi-24 has crashed while on patrol near the southern city of Shiraz, and that the two pilots ejected and survived.

The Sunday report did not say what caused the fighter jet crash, but said an investigation is underway.

Iran signed a contract with Moscow in February to purchase a newer version of the Russian-made fighter jet, the Sukhoi-30.

Iran's air force still relies largely on domestically modified versions of long-outdated warplanes, including Soviet MiGs and American F-14 Tomcats from the 1970s.