"Hundreds of people are missing, according to independent information that has come to us from Tehran since yesterday," he said at a protest meeting in Paris held to denounce the crackdown in Iran.
Lahidji, who is also president of the Iranian League for the Defence of Human Rights, said the information had come from several different sources inside Iran, including from families with members missing or detained.
"That is an estimate, because it is extremely difficult to find out more in Iran at the moment," he noted, adding that around 20 women had been arrested on Saturday "during a peaceful rally in the centre of Tehran."
"A climate of terror and of fear reigns in Iran today," said Lahidji.
Iran has repeatedly accused Britain and the United States of stoking the unrest that swept the country after the June 12 election that returned hardliner Mahmoud Ahmadinejad to power amid complaints it was rigged.
Eight local British embassy staff have been arrested, triggering London's fury and further exacerbating tensions with the West over the post-election turmoil in the Islamic republic.
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