The UK has condemned the arrest of a British ambassador in Tehran as as a “flagrant violation of international law”.

Rob Macaire was detained shortly after attending a vigil for the 176 victims of a Wednesday’s plane crash in Iran, which was caused “unintentionally” by the country’s military who are believed to have mistaken the commercial aircraft for an American jet. 

There has been significant unrest in Tehran since the government admitted the error early on Saturday morning. 

Macaire, who has now been released, said on Twitter that he had left the vigil after some in attendance had began chanting in protest, however was arrested and accused of organising the demonstration. 

He tweeted on Sunday: “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. See comments by Foreign Secretary @DominicRaab.”

Foreign secretary Dominic Raab has condemned the arrest, writing: “The arrest of our ambassador in Tehran without grounds or explanation is a flagrant violation of international law.

“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.”

The incident threatened to re-ignite tensions in the region just as they appeared to be easing.

In an article for The Sunday Telegraph, written before Macaire’s arrest, Raab urged Iran to “come in from the cold” and resolve its differences with the West peacefully.

Following the dramatic events of the past fortnight, he said the “diplomatic door has been left ajar” for the regime in Tehran to end the isolation “choking” its economy.

He said Britain and its European allies still hope to revive the Iran nuclear deal, despite Donald Trump’s insistence that it is dead.

However he said the Iranians must end their pursuit of nuclear weapons, drop their support for terrorism, and release the foreign nationals held as “pawns in its nefarious diplomatic game”. 

Arrest ‘really bad sign’ for jailed Nazanin

The husband of one such detained foreign national – British-Iranian mother Nazanin Zaghari-Ratcliffe – has described the news of the arrest as a “really bad sign for us”.

Richard Ratcliffe said the detention of Macaire did not bode well for his wife, who has been held “essentially as a hostage” for almost four years.

He also said US president Donald Trump’s actions have made the situation “much more volatile” but noted “his administration has got Americans home, whereas the UK hasn’t succeeded”.

Ratcliffe told Sky News’ Sophie Ridge show: “The arrest of the ambassador and the attempt to try and turn that into ‘this is a foreign plot, it’s the British organising the protest’ which is what Iranian Press TV has put out, it’s a really bad sign for us.

“Of course we are in the middle of all that because Nazanin is regularly brought out as someone involved in overthrowing the regime and all those fake stories.

“As a sign of where things are going, the fact the regime’s instinct is A) to deny bad stuff then B) to blame foreigners is not great if you are a foreigner that has been blamed.”

Zaghari-Ratcliffe is serving a five-year sentence over allegations, which she vehemently denies, of plotting to overthrow the Tehran government, having been arrested in 2016 during a holiday visit to show her baby daughter Gabriella, now aged five, to her parents.

She has suffered declining physical and mental health during her detention and suffered panic attacks amid the rising political tensions in recent days.

The 40-year-old is among as many as five people with dual British-Iranian nationality, or with UK connections, believed to be in prison in Iran at present. 

Unrest in Tehran 

In Tehran, riot police have increased their presence on the streets in anticipation of further unrest on Sunday, following the admission that the Ukrainian plane had been shot down “unintentionally”. 

Iranian protesters piled pressure on the country’s leadership after the statement was made early on Saturday morning, with thousands of people gathering – many of whom could be heard chanting “death to the dictator”, directing their anger at Iran’s supreme leader Ali Khamenei.

Reports of the protests were carried by state-affiliated news agencies, while video clips circulated on social media.

 The nation’s press have also issued demands for action. “Apologise and resign,” Iran’s moderate Etemad daily wrote in a banner headline on Sunday, saying the “people’s demand” was for those responsible for mishandling the plane crisis to quit.

All 176 people aboard the flight, many of them Iranians with dual citizenship, were killed.

A spokesperson for the government said on Saturday that the Ukraine International Airlines plane was shot down minutes after take off on Wednesday, when Iranian forces were alert for US reprisals after tit-for-tat strikes.

For days, Iranian officials had vigorously denied it was to blame, even as Canada, which had 57 citizens on the flight, and the US said their intelligence indicated an Iranian missile was to blame, albeit probably fired in error.

Iran’s president said it was a “disastrous mistake” and apologised. But a top Revolutionary Guards commander added to public anger about the delayed admission, when he said he had told the authorities a missile hit the plane the day it crashed.

Another moderate daily Jomhuri-ye Eslami (Islamic Republic) wrote in an editorial: “Those who delayed publishing the reason behind the plane crash and damaged people’s trust in the establishment should be dismissed or should resign.”

Criticism of the authorities in Iran is not unusual, but it tends to stay in narrow boundaries.

The press attacks and protests add to challenges facing the establishment, which in November faced the country’s bloodiest unrest since the 1979 Islamic revolution.

As Saturday’s protests spread across Iran, including major cities such as Shiraz, Isfahan, Hamedan and Orumiyeh, U.S. President Donald Trump said on Twitter: “We are following your protests closely, and are inspired by your courage.”

“There can not be another massacre of peaceful protesters, nor an internet shutdown. The world is watching,” he said, posting his tweets in both Farsi and English.

Protests inside Iran followed a build up of tension between Iran and the United States, which withdrew from Tehran’s nuclear pact with world powers in 2018 and then re-imposed sanctions that have steadily crippled the Iranian economy.

On January 3, a drone strike in Iraq killed prominent Iranian commander Qassem Soleimani, and Tehran responded with missile strikes on U.S. targets in Iraq.

No US soldiers were killed, but in the tense hours after that, the Ukrainian Boeing 737 was cleared to take off from Tehran airport and then brought down by a missile fired in error by an operator who mistook the plane for an attacker.

“Shooting down a civilian aircraft is horrific. Iran must take full responsibility,” Canadian prime minister Justin Trudeau said.

Trudeau said Iranian president Hassan Rouhani had committed to collaborating with Canadian investigators, working to de-escalate tensions in the region and continuing a dialogue.

Iranian officials sought to portray the plane disaster as a second blow to a mourning nation after Soleimani’s death in a U.S. drone strike.

Soleimani’s funeral had prompted huge public gatherings, which the authorities described a show of national unity. But the displays of emotion have been swiftly overshadowed and protesters on Saturday tore up pictures of the slain general.

Public fury at Iran’s authorities had grown as questions about the plane crash mounted. Iranians on social media asked why officials were busy fending off criticism from abroad rather than sympathising with grieving families, whilst others asked why the plane was allowed to take off at a time of high tension.