An engineer, a BP employee and a businessman visiting his family have been identified as the three Britons who were among 176 people killed in a Tehran plane crash.

Western intelligence agencies say they see no sign the Ukraine International Airlines passenger jet, which crashed minutes after take off, was shot down.

Reuters news agency says a Canadian security source has told them that an initial assessment shows the airliner was not brought down by a missile.

All those on board the flight from the Iranian capital's main airport were killed in the crash.

The crash happened hours after Iran launched ballistic missile attacks on two Iraqi bases housing US soldiers, but both Ukrainian and Iranian officials said they suspected a mechanical issue brought down the Boeing 737-800 aircraft.


Image: The plane had only just taken off

One of those who died was Saeed Tahmasebi, from west London, who worked as an engineer for Laing O'Rouke.

A spokeswoman for the company said: "Everyone here is shocked and saddened by this very tragic news.

"Saeed was a popular and well respected engineer and will be missed by many of his colleagues. Our thoughts are with his family and friends at this most difficult time and we will do all we can to support them through it."

Mr Tahmasebi married his Iranian partner, 34-year-old Niloufar Ebrahim, last year. She was also named among the casualties by the Ukrainian airline.

Sam Zokaei, from Twickenham, 42, worked for BP as a senior reservoir engineer but was on holiday.

A BP statement said: "With the deepest regret, we can confirm that one of our colleagues at BP, Sam Zokaei, was a passenger on the Ukrainian International Airlines plane that crashed in Iran this morning, reportedly with no survivors.

"We are shocked and deeply saddened by this tragic loss of our friend and colleague and all of our thoughts are with his family and friends."

A Ukrainian airliner with at least 170 people on board crashed due to technical problems soon after taking off from Tehran

Mohamma Reza Kadkhoda-Zadeh, from near Brighton, was a father-of-one who was on his way back to the UK after visiting his family over the Christmas in his native Iran.

The 40-year-old lived in Brighton and ran a dry cleaning business called Mr Smarty's in nearby Hassocks.

Mr Tahmasebi was a post-graduate researcher with Imperial College London's (ICL) Centre for System Engineering and Innovation.

Before joining ICL the PhD candidate got a degree in civil engineering from the University of Greenwich in 2007 and a masters in structural engineering from the University of Surrey in 2012.

ICL said that Mr Tahmasebi played a leading role on projects including high rise buildings, railways, airports and Ministry of Defence installations, both in the UK and internationally.

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A spokesman for the university added: "We are deeply saddened at this tragic news.

"Saeed Tahmasebi Khademasadi was a brilliant engineer with a bright future.

"His contributions to systems engineering earned respect from everyone who dealt with him and will benefit society for years to come.

"He was a warm, humble and generous colleague, and close friend to many in our community."

Ukraine's foreign minister Vadym Prystaiko said 82 Iranians, 63 Canadians and 11 Ukrainians, including nine crew, were on board.

There were also 10 people from Sweden, four passengers from Afghanistan and three from Germany.

Foreign Secretary Dominic Raab offered his condolences to those affected by the crash.

He said on Twitter: "This is a tragic loss of life for all countries affected. Foreign Office staff are assisting the families of British victims at this difficult time."

The airline said most passengers were in transit and due to connect to other flights on arrival.

Iranian state television said flight PS752 came down due to what it described as "technical problems" after leaving Imam Khomeini airport.

The plane's two black boxes have been recovered but the head of Tehran's civil aviation organisation said it will not be giving them to aircraft manufacturer Boeing.

Image: A child's book was among the wreckage

Ali Abedzadeh said it was not clear which country Iran would send the boxes to so that its data could be analysed, the semi-official Mehr news agency in Iran reported.

Footage showed the wreckage of the plane and smouldering engine parts strewn across a field as rescue workers with face masks recovered bodies of the victims.

The Ukrainian embassy in Tehran originally said engine failure was the cause but a later statement omitted any mention of this.

It said in a second statement that the causes had not been disclosed and that any previous comments were not official.

Asked at a briefing in Kiev if the plane could have been downed by a missile, Mr Honcharuk cautioned against speculation until the results of an investigation were known.

Image: President of Ukraine International Airlines Yevgen Dykhne at a news conference

Ukraine's president Volodymyr Zelenskyy said he had instructed criminal proceedings to be opened over the crash and that the country will test the airworthiness of its entire civilian fleet.

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," said Yevhen Dykhne, president of Ukraine International Airlines.

A Downing Street spokesman said the UK was "working closely with the Ukrainian authorities and the Iranian authorities" over the crash.

The spokesman said there was "no indication" the plane was brought down by a missile, after the Ukrainian authorities refused to rule out the prospect.

A number of 737-800 aircraft have been involved in deadly accidents in recent years.

In March 2016, a FlyDubai 737-800 from Dubai crashed while trying to land at Rostov-on-Don airport in Russia, killing 62.

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 people.

Chicago-based Boeing said it was "aware of the media reports out of Iran and we are gathering more information".