LONDON - Britain has condemned the arrest of the UK ambassador to Iran as a "flagrant violation of international law".
Rob Macaire was detained for a short time on Saturday night after attending a vigil for those who died when Iran's military shot down a passenger plane.
He left the vigil when it turned into a protest but was later accused of helping to organise the demonstrations.
Iran said he was "an unknown foreigner in an illegal gathering" and summoned him to the foreign ministry on Sunday.
In a statement, Iran's foreign ministry said Mr Macaire was "reminded" that his presence at "illegal gatherings contravened" the Vienna Convention on diplomatic relations.
BBC diplomatic correspondent James Landale said Mr Macaire was understood to have protested strongly that his detention was unjustified.
Our correspondent says Mr Macaire made clear any suggestion that he was involved in demonstrations was completely untrue, and he was attending an event advertised as a vigil for the victims of Wednesday's crash - which killed 176 people, including four Britons.
Earlier, Iran's deputy foreign minister Seyed Abbas Araghchi, who denied Mr Macaire was detained, said in a tweet that he thought it "impossible" when police first told him that the UK ambassador had been arrested.
A phone conversation confirmed Mr Macaire's identity and he was released 15 minutes later, Mr Araghchi added.
Mr Macaire has denied taking part in protests and Foreign Secretary Dominic Raab condemned his arrest.
He was arrested and held for three hours when he stopped at a barber shop for a haircut on his way back to the UK embassy.
In a tweet the ambassador said he was attending the vigil because it was "normal to want to pay respects", adding that some of the victims were British.
The ambassador added: "Arresting diplomats is of course illegal, in all countries."(FA)
Rob Macaire was detained for a short time on Saturday night after attending a vigil for those who died when Iran's military shot down a passenger plane.
He left the vigil when it turned into a protest but was later accused of helping to organise the demonstrations.
Iran said he was "an unknown foreigner in an illegal gathering" and summoned him to the foreign ministry on Sunday.
In a statement, Iran's foreign ministry said Mr Macaire was "reminded" that his presence at "illegal gatherings contravened" the Vienna Convention on diplomatic relations.
BBC diplomatic correspondent James Landale said Mr Macaire was understood to have protested strongly that his detention was unjustified.
Our correspondent says Mr Macaire made clear any suggestion that he was involved in demonstrations was completely untrue, and he was attending an event advertised as a vigil for the victims of Wednesday's crash - which killed 176 people, including four Britons.
Earlier, Iran's deputy foreign minister Seyed Abbas Araghchi, who denied Mr Macaire was detained, said in a tweet that he thought it "impossible" when police first told him that the UK ambassador had been arrested.
A phone conversation confirmed Mr Macaire's identity and he was released 15 minutes later, Mr Araghchi added.
Mr Macaire has denied taking part in protests and Foreign Secretary Dominic Raab condemned his arrest.
He was arrested and held for three hours when he stopped at a barber shop for a haircut on his way back to the UK embassy.
In a tweet the ambassador said he was attending the vigil because it was "normal to want to pay respects", adding that some of the victims were British.
The ambassador added: "Arresting diplomats is of course illegal, in all countries."(FA)