Iran's Foreign Ministry has summoned Britain's ambassador to protest the release from prison of the only surviving member of a group of gunmen who seized the Iranian embassy in London in 1980.
British newspapers reported on Friday that Fowzi Nejad, 50, would be freed within days after serving 27 years in jail.
Iran's Deputy Foreign Minister Mehdi Safari summoned British Ambassador Geoffrey Adams on Sunday in protest at a "condemnable and indefensible" act which raised serious questions about Britain's sincerity in its ties with Iran, the
Tehran Timesreported.
The official IRNA news agency said Mr Safari delivered a "strong protest" over the "release of a terrorist," according to BBC monitoring.
Britain's embassy was not immediately available for comment.
Six gunmen seized the Iranian Embassy in London in April 1980, demanding the release of prisoners in Iran and taking 21 hostages, two of whom they killed. The dramatic six-day siege ended when elite SAS troops stormed the building and rescued 19 hostages, killing five gunmen.
Nejad, the only surviving member of the group, was given a life sentence in 1981 but Britain's Guardian newspaper on Friday quoted his lawyer as saying the Parole Board had concluded he was no longer a threat to society and had ruled he could be released.
Britain's
Timesnewspaper reported that Iran wants Nejad returned to Tehran to face trial in connection with the 1980 siege but that Britain had blocked his deportation because it had not received assurances that he might not face the death penalty in Iran.
The Iranian embassy in London said in a statement on Saturday the decision to release Nejad would have "negative impacts on relations" between Iran and Britain.
British officials declined to comment on the case last week.
Britain and Iran are at loggerheads over Iran's nuclear programme, which Tehran says is for peaceful purposes but which the West fears is aimed at developing a nuclear bomb.
In May, Iran's Foreign Ministry summoned Adams to protest a decision by three British judges to uphold a ruling that the British government was wrong to ban an Iranian opposition group as a terrorist organisation.
The People's Mujahideen Organisation of Iran (PMOI) won a seven-year legal battle when three senior judges at Britain's Court of Appeal dismissed a government challenge to the earlier ruling.
Reuters