DUBAI/KIEV • A Ukrainian airliner crashed shortly after take-off from Teheran early yesterday, bursting into flames and killing all 176 people on board.

Debris and smouldering engine parts from the Boeing 737, which carrier Ukraine International Airlines (UIA) said was last serviced two days ago, were strewn across a field south-west of the Iranian capital where rescue workers in face masks laid out scores of body bags.

Passengers' personal items - including cases, clothes, a Santa Claus doll and a boxing glove - were lying amid the debris.

Among the victims were 82 from Iran, 63 Canadians, 11 Ukrainians, 10 Swedes, three Germans and three Britons, Ukrainian Foreign Minister Vadym Prystaiko said. Most passengers were in transit, the airline said.

The accident occurred as confrontation between Iran and the United States threatens to trigger a wider conflict in the Middle East, but officials cautioned that speculation about the cause of the crash was premature.

It was the Kiev-based carrier's first fatal accident, and it said it was doing everything possible to establish what had happened.

Under international rules, responsibility for investigating the crash lies with Iran, and Iranian state television said both of the plane's black boxes had been found.

Iran's aviation authority said it would not hand over the recovered boxes to Americans. "We will not give the black boxes to the manufacturer (Boeing) and the Americans," Iran Civil Aviation Organisation head Ali Abedzadeh said, quoted by Mehr news agency.

"It's not yet clear which country the black box will go to for the investigation," he added.

An amateur video, run by Iranian news agencies and purportedly of the crashed plane, showed a flash in the sky descending rapidly with comments that the aircraft was "on fire", followed by a larger flash as it appeared to hit the ground. The footage has not yet been independently authenticated.

Asked at a briefing in Kiev if the plane could have been downed by a missile, Ukrainian Prime Minister Oleksiy Honcharuk cautioned against speculation before the results of the investigation were known.

Relations between Washington and Teheran are in crisis, with Iran having launched missiles at bases housing US forces in Iraq several hours before the plane crash, in retaliation for a US drone strike last week that killed an Iranian military commander.

Major airlines cancelled Iran and Iraq flights and re-routed others away from both countries' airspace following the Iranian missile strikes.

In Paris, the maker of the plane's engines, French-US firm CFM - co-owned by General Electric and France's Safran - said that any speculation regarding the cause was premature.

Safety experts said airliner accidents are rarely triggered by a single cause and that it typically takes months of investigation to understand all the factors behind them.

An official at Ukraine's embassy in Teheran said that the Iranian authorities had asked it to rescind an initial statement from Iran based on preliminary information that had blamed the accident on engine failure.

Iranian TV said the crash was due to unspecified technical problems, and Iranian media quoted a local aviation official as saying the pilot did not declare an emergency.

Offering "sincere condolences" to relatives of the victims, Ukrainian President Volodymyr Zelensky said he had instructed his prosecutor-general to open criminal proceedings following the crash, without specifying who they would involve. Ukraine would test the airworthiness of its entire civilian fleet of aircraft, he added.

The plane that crashed was a three-year-old Boeing 737-800NG en route to Kiev. Its last scheduled maintenance was on Monday, the airline said.

"The plane was in working order," UIA company president Yevgeniy Dykhne told a briefing in Kiev where he choked back tears. "It was one of our best planes with a wonderful crew."

The airline has suspended its flights to Teheran.

Modern aircraft are designed and certified to cope with an engine failure shortly after take-off and to fly for extended periods on one engine. However, an uncontained engine failure releasing shrapnel can cause damage to other aircraft systems.

Under the rules of the International Civil Aviation Organisation, of which Iran, Ukraine and the US are all members, air crash investigations are led by the country where the accident occurred.

However, according to aviation experts, the countries that are capable of analysing black boxes are few - notably Britain, France, Germany and the US.

France's Accident Investigation Bureau, which handles air crash investigations, said it had not received any request for help from the Iranian authorities after yesterday's crash.

Mr Abedzadeh said: "This accident will be investigated by Iran's aviation organisation but the Ukrainians can also be present during the incident's investigation."

REUTERS, AGENCE FRANCE-PRESSE