BRITAIN's ambassador to Iran was last night arrested after he was accused of "inciting" angry protests in the country's capital, Tehran.
Rob Macaire, 53, was in the furious crowds which clashed with cops and was detained after photographing demonstrators.
Foreign Secretary Dominic Raab said the arrest of the ambassador - who was appointed as envoy in March 2018 - is a "flagrant violation of international law".
He added: "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 deescalate tensions and engage in a diplomatic path forwards."
Mr Macaire was detained for more than an hour before he was released.
The ambassador then denied claims he was involved in any demonstrations.
He tweeted: "Thanks for the many goodwill messages. Can confirm I wasn’t taking part in any demonstrations! Went to an event advertised as a vigil for victims of #PS752 tragedy.
"Normal to want to pay respects- some of victims were British. I left after 5 mins, when some started chanting.
"Detained half an hour after leaving the area. Arresting diplomats is of course illegal, in all countries."
Locals had clashed with riot police as they stormed the streets of Tehran chanting "death to liars" and demanding the country's supreme leader resigns.
The furious crowds' demands for Ayatollah Seyed Ali Khamenei to step down were sparked after the regime admitted it "unintentionally" shot down a Ukranian passenger plane.
Vigils for Iranian lives lost in Tuesday's fatal crash turned angry as protesters hit out at the military blunder.
Riot cops flooded in with tear gas as they tried to break up the large groups outside Amirkabir University, who demanded justice.
Around 1,000 protesters chanted "down with the dictator" and "shame on IRGC [Revolutionary Guard], let the country go".
While at Sharif University, crowds shouted "commander in chief, resign!" as demonstrators ripped up pictures of Qassem Soleimani, commander of the Guard's Quds Force killed in a US drone strike.
The Boeing 737 flight came down on Tuesday, hours after Tehran launched a barrage of rockets against US targets in Iraq.
And Iran claimed the deaths of 176 people were due to the "aggressive" US, which led to the "catastrophic mistake."
After repeated denials, Iran's President Hassan Rouhani admitted his forces gunned down the civilian aircraft because they mistook it for an American fighter plane.
IRAN ADMITS
In a statement, he said: "In an atmosphere of threats and intimidation by the aggressive American regime against the Iranian nation following the martyrdom of general Qasem Soleimani and with the aim of defending against possible US Army attacks, the Islamic Republic of Iran's Armed Forces were on full alert, when unfortunately a human error and miscalculated shooting caused a major catastrophe and dozens of innocent people fell victim to it."
The Iranian leader also offered his "deep condolences" to the families of the victims and said the country's Foreign Ministry would work to identify and bring bodies back to their countries.
Ali Khamenei, the country's supreme leader, has also offered condolences over the plane disaster and called for an investigation.
What we know so far:
- Ukraine Interational Airlines Flight 752 crashed at 6.14am just after leaving Tehran bound for Kiev
- It came down three hours after Iran launched missiles at US bases in Iraq
- Pictures of the wreckage showed telltale shrapnel marks indicating an explosion
- Iran blamed an engine malfunction but refused to hand over black box flight recorders, before admitting the shooting
- Justin Trudeau and Boris Johnson said intelligence points to an Iranian surface-to-air missile
JUSTIN TRUDEAU'S RESPONSE

Canadian Prime Minister Justin Trudeau said Iran must take full responsibility and be held accountable for shooting down a Ukrainian plane and killing all 176 aboard, including 57 Canadians.
Iran admitted earlier on Saturday to having shot down the plane in error.
He said: "What Iran has admitted to is very serious. Shooting down a civilian aircraft is horrific. Iran must take full responsibility.
"Canada will not rest until we get the accountability, justice, and closure that the families deserve."
Earlier military officials reportedly told Iranian state TV they "unintentionally" shot down Ukrainian jetliner they mistook the jet as a hostile target after it turned toward a sensitive center of the Revolutionary Guard.
"The military was at its highest level of readiness," said their statement, referencing the heightened tensions with the United States.
"In such a condition, because of human error and in a unintentional way, the flight was hit," it read.
The Iranian military apologised for the disaster, promising to upgrade their systems to prevent such mistakes in the future.
They said those responsible for the strike on the plane would be prosecuted.
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Iran's acknowledgement of responsibility for the crash is likely to inflame public sentiment against authorities following General Soleimani's killing last week.
The beloved general died in a drone strike ordered by President Trump was seen as a national icon in Iran.
Soleimani was killed days after Iran-backed militias attacked the US embassy in Iraqi capital Baghdad.