BBC director general Mark Thompson said Iran was using 'disturbing tactics'
The BBC has accused the Iranian authorities of "interference and harassment" against journalists at the BBC Persian TV service and their families, ahead of the country's elections next month.
The corporation issued a statement calling on governments and international regulators to put "maximum pressure on Iran to desist in this campaign of intimidation, persistent censorship and a disturbing abuse of power".
Writing on the BBC editors' blog, director general Mark Thompson said: "In recent months, we have witnessed increased levels of intimidation alongside disturbing new tactics. This includes an attempt to put pressure on those who work for BBC Persian outside Iran, by targeting family members who still live inside the country.
"Last week the sister of a BBC Persian member of staff was arrested. She was detained and held in solitary confinement on unspecified charges at Evin Prison in Tehran. Although she has now been released on bail, her treatment was utterly deplorable and we condemn it in the strongest possible terms.
"It is just the latest in a campaign of bullying and harassment by the Iranian authorities, putting pressure on the BBC for the impartial and balanced coverage of events in Iran and the wider region."
Thompson said relatives of other members of BBC Persian staff had been detained by Iranian authorities or had their passports confiscated.
He added: "This issue is wider than the BBC - other international media face similar challenges. But it is behaviour that all people who believe in free and independent media should be deeply concerned about."
The BBC has repeatedly complained of "jamming" - deliberate interference of the Persian channel's broadcast signals - since the service launched three years ago.
Last December, five international broadcasters issued a joint statement calling on regulators to take action against those responsible.
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