Pictures claiming to be taken near the crash site of a Ukrainian airliner that went down in Iran killing all 176 on board appear to show remnants of a rocket.

Images posted on social media that claim to be taken near where the Ukrainian International Airlines plane fell to earth just minutes after take-off show a mysterious piece of debris.

The Boeing 737 jet went down in farmland just outside Parand, a city in Tehran province, after taking off from Imam Khomeini International Airport heading to Kyiv yesterday morning.

Iran claimed the crash was likely to have been caused by 'technical difficulties' and said the pilot lost control after an engine caught fire in mid-air.

They said the pilots made no radio calls and were trying to return to the airport when the plane went down.

And on Wednesday Canadian security sources said a malfunction of the Boeing 737 was the most likely explanation for the crash, citing intelligence from Western countries.

However, authorities in Tehran are refusing to say if they will hand over the black box recorders on board the plane to outside investigators.

Images posted on Twitter by Iranian accounts, showing a charred green section of what appeared to be a rocket with nose-cone, have thrown confusion on what caused the aircraft to crash.

This image was shared online, claiming to be taken in front of a house in Parand, showing a piece of a missile

Alongside the image of what appeared to be a missile, Ashkan Monfared wrote: This is a piece found at the crash site of a Ukrainian passenger plane that fell in front of a resident's home. Does the airplane have anything like this? Isn't it a rocket?'

Witnesses said they heard 'two very loud noises' coming from Parandak garrison moments before the Ukrainian airline crashed in farmland just after take off from Imam Khomeini International Airport. A section of rocket was said to have been found in front of a home in the city of Parand

These unverified pictures were said to show a section of a missile that fell in front of a resident's home in the city of Parand, some 37 miles from Tehran.

Witnesses also posted on Twitter, before it was known that a plane had crashed, describing loud explosions coming from a nearby army base.

The crash site sits just under two miles from Parandak garrison, home to the 23rd Takavar Division of the Islamic Republic of Iran Army.

Alongside a picture of a rocket, that was claimed to be found in a garden of nearby house in Parand, Ashkan Monfared wrote: 'This is a piece found at the crash site of a Ukrainian passenger plane that fell in front of a resident's home. Does the airplane have anything like this? Isn't it a rocket?'

Other witnesses who said they were in the area at the time the aircraft went down said they heard the base had been on alert at the time and described hearing 'two very loud noises'.

One wrote of Twitter: 'I am a resident of Parand and two to three minutes before the plane crashed two very loud noises were heard from Parandak's garrison.'

Video footage appeared to show the plane already burning before it fell out of the night sky, while pictures at the crash site showed the fuselage peppered with mysterious holes.

An aerial view of the crash site on the outskirts of Parand city where rescuers searched the debris with the cause of the crash still unclear

The Ukrainian passenger plane bound for Kyiv appeared to already be in flames before it fell from the sky and into a farm field near Parand, just outside Tehran on Wednesday, sparking speculation it was shot down

Footage from from Iranian State TV showed burning debris at the site of the Ukrainian plane crash, carrying 176 people that crashed shortly after take off

The Boeing plane was less than four years old and had been checked just two days earlier, with 'one of our best crews' manning the aircraft, the Ukrainian airline said.

But the initial assessment by Western intelligence agencies is that the Ukrainian airliner was not brought down by a missile, according to a Canadian security source.

The source, who declined to be identified, said the agencies believed the Boeing 737 plane suffered a technical malfunction.

Three Britons and 63 Canadians were among the 168 passengers and nine crew on board that died on board flight PS752.

The Ukraine International Airliner took off from Tehran airport at 6.10am and disappeared from radars minutes later.

It went down just hours after Iran launched a barrage of missiles at US forces. While the timing of the disaster led some aviation experts to wonder whether it was brought down by a missile, Iranian officials disputed any such suggestion and blamed mechanical trouble.

Ukraine's president Volodymyr Zelenskiy cut short a visit to Oman to return to Kyiv and said a team of Ukrainian experts would go to Tehran to help investigate the crash.

Pieces of debris are seen lying at the crash site in a picture released by an Iranian news agency, showing what appeared to be holes in the fuselage of the Boeing aircraft

Search and rescue workers at the site after the Boeing 737 plane belonging to a Ukrainian airline that crashed near Imam Khomeini Airport in Iran

Major world airlines have rerouted flights crossing the Middle East to avoid danger amid escalating tensions between the US and Iran, and the US Federal Aviation Administration barred American flights from certain Persian Gulf airspace, warning of the 'potential for miscalculation or misidentification' of civilian aircraft.

Ukraine International Airlines President Yevhen Dykhne, said the aircraft 'was one of the best planes we had, with an amazing, reliable crew.'

The jet last underwent routine maintenance on Monday, according to the airline. As for the pilots, it said, 'Given the crew's experience, error probability is minimal. We do not even consider such a chance.'

In Washington, a Democrat who attended a classified briefing from Trump administration officials on Capitol Hill - including Defense Secretary Mark Esper, Secretary of State Mike Pompeo and CIA Director Gina Haspel - said the briefers had no intelligence indicating the plane was shot down.

US aircraft surveillance firm Aireon has collected the position data from the jet and is sharing it with the appropriate authorities, a spokeswoman said.

Aireon's satellite-based global tracking system provides more detailed information than is available on commercial websites like FlightRadar24, which did not capture data at the end of the crashed jet's flight.

Aireon last year provided regulators with more detailed data on the flight path of a crashed Ethiopian 737 MAX jet, leading the United States and Canada to ground the Boeing model based on evidence of similarities to a prior 737 MAX crash in Indonesia.