Talking to state television, the Civil Aviation Organization's Nurollah Rezai Niaraki said that 29 bodies had been recovered from the plane, 43 people were injured, and the rest of the 148 people on board survived unhurt.
He added that some of those injured had been treated as out-patients at Mashhad hospitals.
State television had earlier said that the death toll on the flight to Mashhad from the southern port city of Bandar Abbas was at least 80.
Niaraki also said that since the flight crew survived the crash, a better understanding on the cause of the accident will surface.
Previously state media reported that the Russian-made Tupolev 154, on an internal flight from the southern port of Bandar Abbas, skidded off the runway and crashed into the nearby barriers, leaving gaping holes in the fuselage.
The incident was the latest tragedy to hit Iran's aviation industry, whose fleet is made up largely of Soviet or old Western planes owing to the US sanctions imposed after the Islamic revolution in 1979.
According to figures published in the Iranian media and not counting Friday's accident in Mashhad, more than 1,460 people were killed in 17 air crashes in the past 25 years, including an Iranian plane shot down over the Gulf by a US warship in 1988.
The first television pictures showed the plane, owned by the Iran Airtours carrier, lying flat without its wheels on the outskirts of the airport, with one huge hole burned out in the center of the fuselage.
Rescue workers used hoses to douse the plane, turning the ground around into a quagmire of mud and water. Several corpses were on the ground beside the plane, swathed in blankets.
"As the plane was landing one of its tires burst, forcing it to swerve off the runway before hitting nearby barriers and bursting into flames," an airport official in Mashhad said.
An Iranian civil aviation official was quoted in the media as saying that the plane did not ask for an emergency landing before the accident.
US sanctions mean that Iran can only shop for Airbus or Boeing planes on the used market, and Iranian officials have blamed the blockade for the regular plane crashes in the Islamic republic.
Iranian media are reporting that regular flights have been resumed in Mashhad international airport.
The sanctions cover not only US-made airplanes and spare parts, but also European ones, like Airbus, when they use significant elements of US origin.
Since the 1979 Islamic revolution, Iran has been subject to tough US sanctions that hinder the purchase of critical spare parts for nearly all the planes in its air force, civilian flag carrier Iran Air, and domestic airlines.
In December, 108 people, many of them journalists, were killed when a Lockheed C-130 transport plane crashed in a densely populated area of Tehran. The plane had been bought from the United States before 1979 and was starved of spare parts.
The crash comes as Iran is threatened with further sanctions over its controversial nuclear program after it failed to meet a deadline August 31 to suspend sensitive uranium enrichment work.
Washington expressed sorrow over the plane crash deaths.
"We are sorry to learn of the innocent loss of life in the crash of the TU-154 in Mashhad," State Department spokeswoman Janelle Hironimus said. "We want to send our sincere condolences to all in Iran who lost loved ones in this regrettable accident," she said.
The United States, which is leading a drive to impose UN Security Council sanctions, has predicted that the new penalties will be agreed as early as September.
Media reports have indicated that new sanctions would start with a travel ban for Iranian nuclear officials, ratcheting up later to more severe measures such as restrictions on commercial airline flights.
Iranian transport minister Mohammad Rahamti, quoted by the ISNA news agency, acknowledged that Iran is facing sanctions over the purchasing of Western made planes. He added, however, that "the accident in Mashhad has nothing to do with the age of the plane."
© 2006 Agence France-Presse
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