A spokesman for Aseman Airlines has told state TV that the plane crash in southern Iran has killed all 66 people on board.
An Aseman Airlines ATR-72, a twin-engine turboprop used for short-distance regional flying, went down near its destination of the southern Iranian city of Yasuj, some 485 miles south of the Iranian capital, Tehran.
Aseman Airlines spokesman Mohammad Taghi Tabatabai told state TV that all on Flight No. EP3704 were killed.
"After searching the area, we learned that unfortunately ... our dear passengers had lost their lives," Mr Tabatabai said. "This plane had 60 passengers, 59 adults and one child, as well as a pilot, a co-pilot, two flight attendants and two air marshals on board."
Due to foggy conditions, rescue helicopters could not reach the crash site in the Zagros Mountains, state TV reported. Mr Tabatabai said the plane crashed into Mount Dena, which is about 4,400 meters (14,435 feet) tall.
A commercial plane carrying 66 people has crashed in southern Iran.
The report from the semi-official Fars news agency said the plane crashed near the remote mountain town of Semirom, 620 kilometres (390 miles) south of the capital Tehran.
The report identified the plane as an ATR-72. It said the plane was flying from Tehran to the southern Iranian city of Yasuj.
Under decades of international sanctions, Iran's commercial passenger aircraft fleet has aged, with air accidents occurring regularly in recent years.
Following the 2015 landmark nuclear deal with world powers, Iran signed deals with both Airbus and Boeing to buy scores of new passenger planes.