A spokesperson of the airline told the state TV that the crash killed all 66 people on board.
A spokesman for Aseman Airlines, Mohammad Taghi, reportedly told a state TV channel that all people overseas Flight no. 3704, which included 60 passengers including one child and six members of the flight crew, died in the crash.
There have been scores of plane crashes in Iran since the 1979 Islamic Revolution, mainly because western sanctions for decades limited its ability to purchase spare parts or buy new planes. According to Tasnim news agency, there were 60 passengerson board. However, President Donald Trump's refusal to recertify the deal has injected uncertainty into those sales while Iranians still fly in ageing aircraft.
The plane was carrying 60 passengers, including one child, as well as six crew, Tabatabai said.
One of Iran's worst air accidents happened in February 2003 when an Iranian Ilyushin-76 troop carrier crashed in southeast Iran, killing all 276 Revolutionary Guard soldiers and crew aboard.
"We still have no access to the spot of the crash and therefore we can not accurately and definitely confirm the death of all passengers", Tabatabai told the ISNA news agency.
Iran's President Hassan Rouhani expressed sympathy for all involved, saying, in a statement, that the incident brought "great grief and sorrow".
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He added: "After searches in the area, unfortunately we were informed that the plane crashed".
Footage broadcast on state television showed frantic scenes at the Yasuj airport with families in a state of disbelief. The aircraft had taken off from Tehran with more than an hour's delay due to bad weather and two previous flights had already been cancelled.
On December 6, a military transport craft Lockheed C130 crashed at the foot of a 10-storey apartment building in a residential area of southern Tehran, killing 108 people including 68 journalists and photographers, and injuring more than 90.
Israeli Prime Minister Benjamin Netanyahu offered his condolences over yesterday's crash, just moments after he launched a blistering attack on Tehran's government. It also flies internationally. However, Aseman Airlines is banned from flying in the European Union over safety concerns.
The carrier has a fleet of 29 aircraft, including six ATR aircraft, according to FlightRadar24.
Aseman Airlines has suffered other major crashes with fatalities. Many of Iran's passenger planes are outdated after years of worldwide sanctions, Al Jazeera noted.
A spokesman for ATR, which is part-owned by Europe's Airbus, told AFP "the circumstances of the accident remain unknown" and that worldwide investigators were ready to assist Iran "if needed".
Earlier air disasters include the crash of a Boeing 727 passenger plane in 2011 which killed 78 people in the northwest of Iran, and the 2009 crash of a Caspian Airlines Tupolev aircraft bound for Armenia which killed all 168 people on board.