0303 GMT June 18, 2019
The helicopter went down in Chaharmahal-Bakhtiari Province on its way to pick up a pregnant woman in urgent need of medical care, state television reported.
"Following the request to save the life of a 26-year-old pregnant mother who needed emergency care ... a helicopter was dispatched which unfortunately had an accident," said Pir-Hossein Koulivand, who heads Iran's emergency services.
"Three crewmembers and two first aid workers were martyred", he added.
The crew was dispatched to a mountainous village 30 kilometers from Shahr-e Kord city, emergency services spokesman Mojtaba Khaledi told ILNA.
IRNA said the helicopter collided with a transmission tower.
The Zagros mountain range which passes through Chaharmahal-Bakhtiari has been the site of several crashes in recent years.
A private plane crashed in the area early last year killing all eleven passengers, including the daughter of a prominent Turkish businessman and her friends who were returning from the UAE.
In February 2018, a passenger plane operated by Iran's Aseman Airlines crashed in the Zagros range, killing all 66 people on board.
Iran has suffered a string of plane and helicopter crashes over the past few decades. Tehran says US sanctions have long prevented it from buying new aircraft or spare parts from the West to modernize its fleet.
AFP and Reuters contributed to this story.