Iranian authorities prevented a son of prominent opposition figure Mehdi Karoubi from leaving the country for London and confiscated his passport, Karoubi's website reported on Saturday.
The Sahamnews website said the passport of Mohammad Taghi Karoubi, a university professor, was seized at Tehran's international Imam Khomeini airport on Friday without explanation.
It said he was travelling to London for academic activities, including the re-publication of his book on international law and the use of unilateral force by countries and completion of another.
Karoubi, a pro-reform cleric, came fourth in Iran's disputed presidential poll last June, which the opposition says was rigged to secure hardline President Mahmoud Ahmadinejad's re-election.
The election, which plunged the Islamic Republic into deep political turmoil, was followed by huge street protests and thousands of opposition supporters were detained.
The authorities rejected opposition charges of vote fraud and portrayed the protests as a foreign-backed bid to undermine the country's Islamic system of government.
