Alireza Akbari, a British-Iranian dual national and former deputy defence minister to Iran, has been executed after being accused of spying for the UK.
The former deputy was previously arrested in 2019 and convicted of working against the state for a foreign power, something he denied.
Akbari's family had also been asked to visit him for a "final time" on Wednesday with his wife saying he had been moved into solitary confinement.
The UK had called on the Persian nation to stop the execution and "immediately release him."
Iran must halt the execution of British-Iranian national Alireza Akbari and immediately release him.
— James Cleverly🇬🇧 (@JamesCleverly) January 11, 2023
This is a politically motivated act by a barbaric regime that has total disregard for human life.
On Friday, James Cleverly, the UK's Foreign Secretary warned that "Iran must halt the execution of British-Iranian national Alireza Akbari and immediately release him.
"This is a politically motivated act by a barbaric regime that has total disregard for human life."
Later telling Iranian authorities that the UK is "watching the case of Alireza Akbari closely."
Prime Minister Rishi Sunak expressed his disgust at the move by Iran, saying on Twitter: "I am appalled by the execution of British-Iranian citizen Alireza Akbari in Iran.
"This was a callous and cowardly act, carried out by a barbaric regime with no respect for the human rights of their own people. My thoughts are with Alireza’s friends and family."
Ahead of the execution, Iran released a video of Akbari, showing what looked to be forced confessions.
However, BBC Persian broadcasted an audio message on Wednesday in which Akbari was tortured and forced to confess to crimes he did not commit.
The United States of America also joined the UK's calls to stop the execution with US diplomat Vedant Patel saying: "his execution would be unconscionable."
Adding: "the charges against Alireza Akbari and his sentencing were politically motivated."
Earlier in the week, the UK Foreign Office told the BBC that it had been supporting Akbari's family and repeatedly raising the case with Iranian authorities.
It requested consular access but this was rejected with Iran not recognising dual nationality for Iranian citizens.
In recent years, Iran has arrested dozens of Iranians with dual nationality and foreign permanent residency largely over allegations of espionage.
This comes as Nazanin Zaghari-Ratcliffe and Anoosheh Ashoori were allowed to leave Iran after the UK settled an outstanding debt with the nation.
However, at least two more British nationals remain in detention in Iran.
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