JANNAT ABAD, Iran (Reuters) - A Tupolev aircraft crashed in Iran on Wednesday on its way to Armenia after catching fire in mid-air and plowing into farmland, killing all 168 people on board just 16 minutes after take-off.

In the worst crash in Iran for six years, the Russian-built Caspian Airlines plane left only scattered bits of incinerated metal and fragments of the bodies of 153 passengers and 15 crew across a wide area around a deep smoking crater in the ground.

The Tu-154 plane, flying to Armenia’s capital Yerevan from Tehran, crashed near the northwestern city of Qazvin shortly before noon (0730 GMT). Officials said they would not know why it crashed until the black box flight recorders have been found.

Eight members of Iran’s national junior judo team and two coaches were among the dead as well as a former Iranian MP representing Iran’s Armenian minority and, reportedly, the wife of the head of Georgia’s diplomatic mission in Iran.

“I saw a finger of a passenger on the ground. There is no sign of the airplane, just small pieces of metal,” said a Reuters witness. “I do not see even a complete leg or arm.”

Weeping relatives and friends gathered at Yerevan airport where a notice on a wall listed people who were on board. Doctors treated relatives for shock and heart problems.

Six Armenian and two Georgian citizens were on board, the deputy head of the Armenian civilian aviation authority Arsen Poghosyan told a media briefing at Yerevan Airport. Two crew and 29 passengers were Iranian citizens with ethnic Armenian backgrounds, he said.

Iran is home to some 100,000 ethnic Armenianns, many of whom frequently fly between Tehran and Yerevan to visit relatives.

Fina Karapetian, an Armenian in her 30s, said her sister and two nephews, 11 and 6, were on board the crashed plane. “I heard everyone in the aircraft has died. What will I do without Armen and Vahe?” she said, before fainting.

TOTALLY DESTROYED

Security forces held back distraught relatives who tried to break through the cordon at the site to find loved ones’ bodies.

“The Tupolev plane has been totally destroyed and the corpses, unfortunately, have been totally burned and destroyed,” Qazvin police commander Massoud Jafarinasab told semi-official Fars news agency.

A local official said the aircraft had technical problems and tried to make an emergency landing. “Unfortunately the plane caught fire in the air and it crashed,” he told Fars.

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One witness said he had seen the plane on fire in the air, trying to land. “It made circles in the air. Then I heard an explosion,” Mostafa Babashahverdi, a farmer, told Reuters.

“We found severed heads, fingers and passports of the passengers,” he said.

State radio said the pilot had made no mention of any technical problem in a taped conversation with a control tower.

Slideshow ( 29 images )

Search teams picked through a wide area of 200 sq meters at the crash site about 150 kilometers (93 miles) north of Tehran.

“What rescuers found was bodies all ripped apart,” a team member said. “We are just collecting smashed flesh in bags.”

Gocha Gvaramadze, an official from the Georgian embassy in Armenia, told Rustavi-2 television channel, “As far as we know, there were two Georgian citizens onboard. One was our embassy’s financial manager and another -- a wife of the head of Georgia’s diplomatic mission in Iran.”

Yerevan airport officials said an aircraft would take relatives to visit the site. President Mahmoud Ahmadinejad has ordered a special task force to investigate the crash. Armenia’s President Serzh Sarksyan declared by decree that July 16 will be a national day of mourning for the crash victims.

U.S. sanctions bar the sale of Boeing aircraft to Iran and hinder the Islamic republic buying other aircraft or spares from the West, many of which rely on U.S.-built engines and parts.

Air safety experts have said Iran has a poor record, with a string of crashes in the past few decades -- many involving Russian-made aircraft. It was the third deadly crash of a Tupolev Tu-154 in Iran since 2002.

It was the deadliest crash since 2003 when an Ilyushin Il-76, also Russian built, crashed into an Iranian mountain.

Tehran-based Caspian Airlines was set up in 1993 and flies an all-Tupolev fleet linking Iranian cities and also routes to the United Arab Emirates, Ukraine and Armenia.