Image copyright Reuters Image caption Friends of high school student Arad Zarei held pictures of him at a vigil for victims of the Iran plane crash in Toronto

A teenager who was brought up in London was among the 176 people killed when a Ukrainian passenger jet crashed in Iran, it has emerged.

Arad Zarei, 17, who relocated to Canada after attending St Mary's Primary School in Twickenham until 2014, was said to be visiting his mother.

The prime minister said four Britons are known to have died in the crash.

The Foreign Office has hardened its advice to warn Britons against all travel to, from and within Iran.

A spokesman for Arad Zarei's former school said staff and governors were "shocked and immensely saddened" to hear of his death in the plane crash.

"Arad attended St Mary's until 2014 and is remembered fondly by his teachers.

"We wish to extend our prayers and condolences to Arad's family and friends at this time."

Missile claims

The crash on Wednesday came just hours after Iran carried out missile strikes on two airbases housing US forces in Iraq.

The air strikes were in retaliation for the US killing of top Iranian general Qasem Soleimani.

Western leaders, including Prime Minister Boris Johnson, have said evidence suggested the plane was hit by a surface-to-air missile, possibly in error - something Iran denies.

Image copyright Reuters Image caption Dominic Raab, [left] pictured at a news conference in Montreal, has said victims' families deserve to know the "truth" about what happened

Echoing comments by Mr Johnson, Foreign Secretary Dominic Raab called for a thorough investigation, saying Iran should "open up" the crash site to international investigators, adding that grieving families deserved the "truth".

Also on board the flight from Tehran were 82 Iranians, 63 Canadians, 11 Ukrainians, 10 Swedes, four Afghans and three Germans.

The names of three Britons who died in the crash have been released so far.

Image copyright Facebook/LinkedIn Image caption British nationals Mohammed Reza Kadkhoda Zadeh, Sam Zokaei and Saeed Tahmasebi died in the crash

Mohammed Reza Kadkhoda Zadeh, 40, who ran a neighbourhood dry cleaners in Hassocks, West Sussex, had a nine-year-old daughter.

BP engineer Sam Zokaei, 42, from Twickenham, and PhD student Saeed Tahmasebi, 35, who worked as an engineer for Laing O'Rourke in Dartford, were also killed.

Last year, Mr Tahmasebi - whose full name was Saeed Tahmasebi Khademasadi - married his Iranian partner, Niloufar Ebrahim, who was also listed as a passenger on the plane.

Media playback is unsupported on your device Media caption Richard Ratcliffe says the fallout from US-Iran tensions is a taking a toll on his wife

Meanwhile, concerns have been raised for Britons detained in Iran, amid the growing tensions.

Richard Ratcliffe, husband of Nazanin Zaghari-Ratcliffe, a charity worker from London who has been detained for more than three years over spying allegations she denies, held a meeting with Foreign Office officials on Friday.

He told the BBC the prime minister raised the cases of detained Britons when he spoke to Iranian President Hassan Rouhani on Thursday.

"This is a situation where there is a lot of anger in Iran and a lot of vulnerability, and it's very stressful for the people involved," he added.

"Nazanin was taken down to the clinic overnight two nights ago, through palpitations and panic attacks.

"So I think it's important for the government to just do what they can."

Media playback is unsupported on your device Media caption Mobile phone footage appears to show the plane in the moments before it came down

The wife of Anoosheh Ashoori, a British-Iranian dual national who has been in jail for more than two years over espionage charges which he denies, called on the UK government to do more to protect her husband.

Sherry Izadi said she was worried there could be a backlash against foreign prisoners.