Britain’s ambassador to Iran, Rob Macaire, has been arrested and held for several hours after attending a vigil for the victims of the Ukraine air plane crash which turned into demonstration.
Details of his arrest were announced by the country’s semi-official Tasnim news agency.
News of his arrest prompted an angry response from Foreign Secretary, Dominic Raab.
"The arrest of our Ambassador in Tehran without grounds or explanation is a flagrant violation of international law,” he said.
"The Iranian government is at a crossroads 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."
It is understood that the event which Mr Macaire attended had been advertised as a vigil at Amir Kabir University for the 176 victims of the Tehran plane crash last week.
He and another member of the embassy staff left once the vigil turned into a protest.
Mr Macaire was arrested on his way back to the embassy after getting a haircut. He was held for three hours before being released, following the intervention of the Iranian foreign ministry.
The Tasnim news agency claimed Mr Macaire was in the midst of the rally accusing him of trying to “organise, instigate and direct some of the radical and destructive actions.”
It said Mr Macaire, who was safely back at the embassy, is to be summoned and prosecuted on Sunday.
Mr Macaire, who speaks Farsi, has been the UK ambassador to Iran since April 2018, succeeding Nicholas Hopton.
An Oxford history graduate, Mr Macaire, 53, joined the Foreign Office in 1990.
On taking his appointment Mr Macaire said he wanted to maintain Britain's continued engagement with Iran, which he described as "vital to our goal of making the Middle East region a safer and more stable place."
He added that he looked forward "to working with the Government of Iran and with international partners to preserve the nuclear deal and deepen our bilateral relationship, through constructive engagement on human rights, trade, and seeking political solutions to the conflicts in Yemen, Syria and elsewhere.”
He previously served in Bucharest, Washington, New Delhi and in Nairobi where he was appointed British High Commissioner.
Mr Macaire, who is married with two daughters, previously he worked at the Ministry of Defence and also had a stint in the private sector, assuming the role of Director of Government/Public Affairs and Political Risk at BG Group plc.