Ukraine's foreign minister says that Iranian, Canadian, Ukrainian, Swedish, Afghan, British and German nationals were killed in the Ukrainian plane crash just outside Tehran.
Foreign Minister Vadim Prystaiko said after Wednesday's crash that there were 82 Iranians, 63 Canadians and 11 Ukrainians on board.
The Ukrainian nationals included two passengers and nine crew members. He says there were also 10 Swedish nationals, four Afghans, three Germans and three British nationals.
Airline officials said most of the passengers were transiting through Kyiv to other destinations.
The Boeing 737 jet came down just three minutes after take-off from Imam Khomeini International Airport, sparking fresh alarm in the region just hours after Iran launched a missile attack on US bases in Iraq.
The unofficial list of nationalities were:
• Iran - 82
• Canada - 63
• Ukraine - 11
• Germany - 3
• Great Britain - 3
• Sweden - 10
• Afghanistan - 4
There were conflicting reports on the numbers and it is believed that a number of the passengers may have had dual citizenship.
There were no survivors, Ukrainian president Volodymyr Zelensky said.
Video footage tweeted by the BBC's Iran correspondent, Ali Hashem, appeared to show the plane already burning in the sky before it crashed in a massive explosion.
It sparked speculation that the jet could have been shot down accidentally by nervous Iranian air defence soldiers, hours after Iran fired 22 ballistic missiles at US bases in retaliation for the killing of general Qassem Soleimani.
Just hours before the crash, the US Federal Aviation Administration had banned US airlines from flying over Iran, Iraq and the waters of the Persian Gulf due to the Middle East crisis.
However, the Ukrainian embassy in Tehran reported that the crash had been caused by an engine failure rather than terrorism.
Iranian officials said the pilot had lost control of the Boeing jet after a fire struck one of the plane's engines, but said the crew had not reported an emergency and did not say what caused the fire.
Zelenskiy extended his condolences to the families of the victims. His office said he had cut his visit to Oman short and was returning to Kyiv because of the crash. The country's Prime Minister Oleksiy Honcharuk confirmed the casualty toll.
"Our task is to establish the cause of the crash of the Boeing and provide all necessary help to the families of the victims," said parliament speaker, Dmytro Razumkov, in a Facebook statement.
Ukraine International Airlines said it had indefinitely suspended flights to Tehran after the crash.
"It was one of the best planes we had, with an amazing, reliable crew," Yevhen Dykhne, president of the Ukraine International Airlines, said at a briefing following the crash.
The plane had been delayed from taking off from Imam Khomeini International Airport by almost an hour. It took off to the west, but never made it above 8,000 feet in the air, according to data from the flight-tracking website FlightRadar24.
It remains unclear what happened.
Qassem Biniaz, a spokesman for Iran's Road and Transportation Ministry, said it appeared a fire struck one of its engines. The pilot of the aircraft then lost control of the plane, sending it crashing into the ground, Biniaz said, according to the state-run IRNA news agency.
Hassan Razaeifar, the head of air crash investigation committee, said it appeared the pilot couldn't communicate with air-traffic controllers in Tehran in the last moments of the flight. He did not elaborate.
Ukrainian authorities have offered to help with the investigation of the plane crash.
"We're preparing a group of specialists in order to help with the search operation and the investigation of the cause of the crash," Honcharuk said.
The plane, fully loaded with fuel for its 2300-kilometre flight, slammed into farmland near the town of Shahedshahr on the outskirts of Tehran.
Videos taken immediately after the crash show blazes lighting up the darkened fields before dawn.
Resident Din Mohammad Qassemi said he had been watching the news about the Iranian ballistic missile attack on US forces in Iraq in revenge for the killing of Revolutionary Guard Gen. Qassem Soleimani when he heard the crash.
"I heard a massive explosion and all the houses started to shake. There was fire everywhere," he told The Associated Press.
"At first I thought (the Americans) have hit here with missiles and went in the basement as a shelter. After a while, I went out and saw a plane has crashed over there. Body parts were lying around everywhere."
The plane carried 167 passengers and nine crew members from different nations on its flight to the Ukrainian capital, Kyiv, Biniaz said.
The majority of the passengers were Iranian nationals, Russia's RIA Novosti agency reported, citing Iranian authorities.
Staff at the Boryspil airport in Kyiv, where the plane was headed, told the AP that passengers on this flight are usually Iranian students coming back to Ukraine after winter holidays.
AP journalists who reached the crash site saw a wide field of field of debris scattered across farmland, the dead laying among shattered pieces of the aircraft.
Their possessions, a child's cartoon-covered electric toothbrush, a stuffed animal, luggage and electronics, stretched everywhere.
Rescuers in masks shouted over the noise of hovering helicopters as they worked. They quickly realised there would be no survivors.
"The only thing that the pilot managed to do was steer the plane towards a soccer field near here instead of a residential area back there," witness Aref Geravand said.
"It crashed near the field and in a water canal."
The Boeing 737-800 is a very common single-aisle, twin-engine jetliner used for short to medium-range flights. Thousands of the planes are used by airlines around the world.Introduced in the late 1990s, it is an older model than the Boeing 737 MAX, which has been grounded for nearly 10 months following two deadly crashes. Boeing built the aircraft that crashed Wednesday in 2016 and it last underwent routine maintenance on Monday, Ukraine International Airlines said.
A number of 737-800 aircraft have been involved in deadly accidents over the years.In March 2016, a FlyDubai 737-800 from Dubai crashed while trying to land at Rostov-on-Don airport in Russia, killing 62 onboard. Another 737-800 flight from Dubai, operated by Air India Express, crashed in May 2010 while trying to land in Mangalore, India, killing more than 150 onboard.
- additionla reporting AP