Before crashing, the plane's tail was on fire as it circled in the air, one witness told The Associated Press.
"Then, I saw the plane crashing nose-down. It hit the ground causing a big explosion. The impact shook the ground like an earthquake. Then, plane pieces were scattered all over the agricultural fields," Ali Akbar Hashemi, a 23-year-old who was laying gas pipes in a nearby home, told AP by phone.
The impact blasted a deep trench in the dirt field, which was littered with smoking wreckage, body parts and personal items from the Tupolev jet, according to photos from the scene. Firefighters put out the flaming wreckage, which officials said was strewn over a 200 yard area. A large chunk of a wing was visible in footage of the scene, but much of the wreckage appeared to be in small shreds.
The Russian-made Tupolev 154 is a Soviet-era workhorse, but the passenger jet has a less-than comforting safety record, reports CBS News correspondent Richard Roth, and Iran has often been criticized for poor plane maintenance.
Roth reports that Iran has complained that its aviation safety is compromised by U.S. and international trade sanctions. The U.S. sanctions prevent Iran from updating American aircraft bought before the 1979 Islamic revolution and make it difficult to get European spare parts or planes as well.
Iranian airlines and the military have turned increasingly to Russian aircraft, which are not affected by sanctions, but have seen a string of accidents. Two other Tupolev crashes in Iran this decade have killed nearly 140 people.
The Caspian Airlines Tu-154M jet had taken off from Tehran's Imam Khomeini International Airport on Wednesday morning and was headed to the Armenian capital Yerevan. It crashed at 11:30 am about 16 minutes after takeoff near the village of Jannat Abad outside the city of Qazvin, around 75 miles northwest of Tehran, civil aviation spokesman Reza Jafarzadeh told state media.
At Yerevan's airport, Tina Karapetian, 45, said she had been waiting for her sister and the sister's 6- and 11-year-old sons, who were due on the flight. "What will I do without them?" she said, weeping, before she collapsed to the floor.
The cause of the crash was not immediately known. Hossein Ayaznia, an aviation police official, said emergency workers were searching for the plane's data recorders to get evidence of the cause.
Iran's Jafarzadeh and the deputy chairman of Armenia's civil aviation authority Arsen Pogosian said there were 153 passengers and 15 crewmembers on board the plane. "In all likelihood, all on board were killed," Pogosian told reporters at Yerevan airport.
Most of the passengers were Iranians, many of them from Iran's large ethnic Armenian community, along with six Armenian citizens and two Georgian citizens, Pogosian said. The two Georgians included a staffer from the Caucasus nation's embassy in Yerevan, Georgia's military attache in the Armenian capital said.
Serob Karapetian, the chief of Yerevan airport's aviation security service, said the plane may have attempted an emergency landing, but reports that it caught fire in the air were "only one version." He did not elaborate. A police official told Iran's semi-official ISNA news agency that several witnesses reported seeing the plane's tail on fire in the air as it circled to find a place to land.
The plane was completely destroyed in the crash and shattered to pieces, Qazvin emergency services director Hossein Behzadpour told the state news agency IRNA.
"The force of the crash was so serious that pieces of the aircraft were thrown over a 200 meter area. Unfortunately, all the bodies were totally destroyed," Behzadpour said.
President Mahmoud Ahmadinejad issued a statement expressing condolences "to the supreme leader Ayatollah Ali Khamanei and the families of the dead" over what he called a "heart-wrenching tragedy" and ordered an investigation into the cause. Armenia's president, Serge Sarkisian, also expressed his condolences and declared Thursday a day of mourning.
Also among the passengers were eight members of Iran's national youth judo team, along with two trainers and a delegation chief, who were scheduled to train with the Armenian judo team before attending competitions in Hungary on Aug. 6, state TV said.
The crash is the worst since February 2003, when a Russian-made Ilyushin 76 carrying members of the elite Revolutionary Guards crashed in the mountains of southeastern Iran, killing 302 people aboard.
Caspian Airlines is an Iranian-Russian joint venture founded in 1993 whose fleet is made up of Tupolevs.
Soviet-built Tupolev and Antonov planes have long been the mainstays of the civil air fleets in Russia and former Soviet republics. Once considered reliable aircraft, the most widely used models - like the Tu-154 - have in recent years gone largely unmodified or updated by aircraft designers.
The Soviet collapse resulted in the sharp decline in government funding for aircraft spare parts manufacturers and for the aircraft manufactures themselves, and many airlines fell behind in maintenance programs for the planes.
Iran has about a dozen Soviet-built Tu-154 airliners. In 2006, Russia negotiated the sale of five Tu-204s to Iran.
In February 2006, a Russian-made Tu-154 operated by Iran Airtour, which is affiliated with Iran's national carrier, crashed during landing in Tehran, killing 29 of the 148 people on board. Another Airtour Tupolev crashed in 2002 in the mountains of western Iran, killing all 199 on board.
The crashes have also affected Iran's military. In December 2005, 115 people were killed when a pre-1979 U.S.-made C-130 plane, crashed into a 10-story building near Tehran's Mehrabad airport. In Nov. 2007, a Russian-made Iranian military plane crashed shortly after takeoff killing 36 Revolutionary Guards members.