State broadcaster IRIB earlier said there were 10 people on the plane, without confirming any casualties.
Local media is reporting that 15 of the plane's crew were killed when the plane hit the ground and burst into flames.
The airport is located near Karaj in the central province of Alborz.More news: GOP Sen. Lindsey Graham: Trump isn't giving in on southern border wall
The aircraft, which bore the paint scheme of the Iranian air force's Saha civilian airline, was making emergency landing around 8:30 a.m. Monday at Fath Airport, an airfield controlled by Iran's powerful paramilitary Revolutionary Guard. The army's statement came after some confusion over who owned the plane. However a spokeswoman for the Manas airport in Kyrgyzstan said the plane belonged to Iran's Payam Air.
"We do not know yet whether it was an Iranian or foreign cargo plane", a local official told TV.
Iranian state television showed pictures of a plume of smoke rising from the crash site and said rescue teams had been sent to the area.More news: The Best Fiber-Rich Foods To Reduce Chronic Illness Risks
Iran's air force said in a statement that the fate of the crew, including their possible "martyrdom", was under investigation.
Iranians often use the word "martyrdom" for those who die in war or national service, suggesting the aircraft may have belong to the air force.More news: Game of Thrones Season 8 to premiere on April 14