Britain's ambassador to Iran was arrested during protests in Tehran after the country admitted it had "unintentionally" shot down a Ukrainian passenger plane.

Rob Macaire was detained on suspicion of organising, provoking and directing radical actions, with hostility towards Supreme Leader Ayatollah Ali Khamenei having grown since the announcement earlier on Saturday.

Mr Macaire was released after more than an hour in custody as the demonstrations went on, with videos on social media from the capital showing hundreds of people chanting "death to the liars" and for the supreme leader to resign.

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Foreign Secretary Dominic Raab called Mr Macaire's arrest a "flagrant violation of international norms".

"The Iranian government is at a cross-roads moment. It can continue its march towards pariah status with all the political and economic isolation that entails, or take steps to de-escalate tensions and engage in a diplomatic path forwards," he said.


Image: The UK's ambassador to Iran, Rob Macaire. Pic: Foreign Office

The admission by Iran over what caused Ukraine International Airlines flight PS752 to crash confirmed Western intelligence that the plane was struck by a short-range missile not long after take-off from Tehran International Airport, killing all 176 passengers and crew.

Most of the victims were from Iran and Canada, with four from Britain, and Canadian Prime Minister Justin Trudeau and his British counterpart Boris Johnson are among the world leaders to have demanded a full investigation.

Image: Students are among those demonstrating in Tehran

Image: Many have held up radical slogans demanding regime change

According to the Iranian Fars news agency, demonstrators ripped up pictures of Major General Qassem Soleimani, whose controversial assassination by the US prompted Iran to target two American bases in Iraq.

Those strikes came just hours before the Ukrainian plane was shot down on Wednesday, with Iranian forces having remained on high alert for possible retaliation from the US.

Khamenei, who was seen crying at the funeral of the commander earlier this week, has expressed "deep sympathy" to the victims of the plane crash and other senior officials have also apologised.

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But US Secretary of State Mike Pompeo has tweeted that the protests were a sign that the Iranian people "are fed up with the regime's lies, corruption, ineptitude and brutality".

US President Donald Trump also expressed his support of "the brave, long-suffering people of Iran" and called on the Iranian government to allow human rights groups to monitor the protests.

To the brave, long-suffering people of Iran: I've stood with you since the beginning of my Presidency, and my Administration will continue to stand with you. We are following your protests closely, and are inspired by your courage. — Donald J. Trump (@realDonaldTrump) January 11, 2020

The government of Iran must allow human rights groups to monitor and report facts from the ground on the ongoing protests by the Iranian people. There can not be another massacre of peaceful protesters, nor an internet shutdown. The world is watching. — Donald J. Trump (@realDonaldTrump) January 11, 2020

Iran had previously insisted it had nothing to do with the plane crash.

Mr Trudeau has said "there are still questions that must be answered" about how and why the plane was shot down.

Speaking at a media conference, Mr Trudeau demanded a "full and complete investigation" into the crash.

"Shooting down a civilian aircraft is horrific and Iran must take full responsibility," he said.

Image: Iranian Supreme Leader Khamenei (left) weeps as he leads a prayer over the coffin of Qassem Soleimani

Asked about whether the killing of the Soleimani had contributed to the plane crash, Mr Trudeau said: "Times of tension like these is when a tragedy like this crash can happen."

He called for a "de-escalation of tensions" in the region, and also condemned the Iranian strikes on the US air bases, which housed Canadian troops.

"The reality is there have been significant tensions in that region for a long time," Mr Trudeau said.

"We are calling for a de-escalation to ensure there are no more tragic accidents and loss of civilian life."

Image: Pictures of the wreckage were shared by the Office of the President of Ukraine

Image: The site where the plane crashed

Mr Trudeau welcomed Iran's admission, describing it as "an important step towards providing answers for families", however he said he and other leaders "still have questions that must be answered".

He added: "Families are seeking justice and accountability and deserve closure."

Image: Justin Trudeau has attended vigils for victims of the crash

His call for an investigation echoed that of Mr Johnson, who said Iran must cooperate.

Mr Johnson added: "This tragic accident only reinforces the importance of de-escalating tensions in the region. We can all see very clearly that further conflict will only lead to more loss and tragedy. It is vital that all leaders now pursue a diplomatic way forward."

Both leaders have spoken on the phone with Iranian President Hassan Rouhani.

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Ukrainian President Volodymyr Zelenskiy also spoke with his Iranian counterpart on Saturday, reiterating his demand that those behind the crash "must be held accountable" and that the victims be repatriated "immediately".

Meanwhile, the EU Aviation Safety Agency has urged European airlines to avoid Iranian airspace until further notice.

Image: A plane engine among debris from the crash

Tehran has said the Ukrainian plane was "misidentified as a cruise missile" by an air defence operator.

The supreme leader was reportedly informed on Friday and ordered the information be made public, despite senior officials having spent days denying that Iran was responsible for the accident.

Tehran went as far as to say that accusations by the US and Canada that Iran had downed the jet, citing intelligence, amounted to "psychological warfare against Iran".

Image: Mourners console each other during a vigil in Toronto

On Friday, Hamid Baeidinejad, the Iranian ambassador to the UK, told Sky News that he was confident there had not been a missile strike that caused the plane to come down.

After Iran's admission, Ayatollah Khamenei said: "Having been informed about the crash of the Ukrainian passenger plane and confirmation of the human error, the tragedy of deaths of passengers in this sad incident became a lot more severe for me."

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As well as in Tehran, there have also been anti-regime protests over the plane crash in other Iranian cities.

Those include Shiraz, Isfahan, Babol, Abdan, Mashhad and Hamedan.

Ayatollah Khamenei is not the only target for the demonstrators - some are also chanting against the military and the danger of potential war with the US.