The Russian-built jet was carrying 147 people from the port city of Bandar Abbas in the south, state TV said.
Reports say dozens of people managed to escape the blaze in Mashhad, a popular destination for Shia pilgrims.
The fire began when the Tu-154 left the runway on landing at 1345 (1015 GMT), possibly because of a burst tyre.
Television pictures show a broken, partially charred plane lying on the side of a runway, as firefighters damp down the smouldering wreck.
The head of the airport in Mashhad, named only as Mr Esmail, told Iranian TV that up to 60 people had been rescued.
"The latest report puts the number of survivors at 50 to 60," he said.
"The report says that 70 to 80 people have unfortunately lost their lives."
He added that he did not have an exact number for the people on the flight but the airline thought the Tu-154 was carrying "about 140".
A spokesman for Iran's Civil Aviation Organisation, Reza Jafarzadeh, said the cause of the incident was still not clear.
Air disaster history
The BBC's Tehran correspondent, Frances Harrison, says Mashhad, which lies 1,000 km (620 miles) north-east of the capital, is a major pilgrimage destination for devout Shia as it houses the shrine of Imam Reza.
Iran has a terrible record of airline safety, our correspondent says.
One reason for this is US sanctions, which prevent the Iranian government from buying spare parts for its ageing fleet or purchasing new aircraft from major aviation companies in the West, she adds.
Planes from the airline involved, Iran Air Tours, crashed in 2002, 1993 and 1992 - on all occasions, there were no survivors.
The Tupolev-154 has for more than a quarter of a century been the backbone of Russian and Soviet air transport.
According to Paul Duffy, Russian editor of Air Transport World, few Tu-154 accidents appear to have involved technical failure.
Source:BBCGüncelleme Tarihi: 20 Eylül 2018, 18:16