Iranian authorities have arrested at least 24 journalists and bloggers since postelection protests began a week ago, and a media watchdog says reporters are a "priority target" for Iran's leadership.
Among those detained were the head of the Association of Iranian Journalists and a Canadian reporter for Newsweek. The British Broadcasting Corporation's correspondent has been ordered to leave the country.
"It's becoming more and more problematic for journalists," said Benoit Hervieu of Paris-based Reporters Without Borders, also known by its French acronym RSF.
The group released the names of 24 Iranian journalists, editors and bloggers arrested since June 14, and says it has lost contact with several others believed detained or in hiding. Hervieu said RSF verified each arrest via its network of reporters and activists in Iran.
Newsweek said in a statement later that its correspondent Maziar Bahari, a Canadian citizen, was detained without charge Sunday morning and has not been heard from since. Newsweek defended his coverage of Iran as "fair and nuanced" and called for his release.
In most cases, the reasons behind the detentions remain unclear.
Iran's authorities have long kept a close eye on local and international media operating in the country, and clamped down as protests engulfed Tehran last week over the June 12 presidential election, the biggest challenge to the cleric-led government in 30 years. President Mahmoud Ahmadinejad was declared the landslide winner, but supporters of reformist challenger Mir Hossein Mousavi say fraud was widespread.
Authorities have banned foreign media from reporting from the street and allow only phone interviews and information from officials sources such as state TV. Many Web sites have been blocked. Iran is particularly sensitive about news reports, blogs and Internet reports in Farsi.
"The regime has been visibly shaken by its own population and does not want to let this perception endure," RSF said in a statement.
The BBC's Jon Leyne has been ordered to leave the country, a BBC spokesman said on condition of anonymity in line with company policy.
The Fars news agency said Sunday that Leyne will have to leave Iran within 24 hours, and that Iranian officials have accused him of "dispatching fabricated news and reports, ignoring neutrality in news, supporting rioters and trampling the Iranian nation's rights."
Ali Mazroui, the head of the Association of Iranian Journalists, was arrested Sunday morning, RSF said. Overnight, husband-and-wife Bahaman Ahamadi Amoee and Jila Baniyaghoob were arrested by plainclothes officers who searched their home, RSF said.
Baniyaghoob edits a news Web site that focuses on women's rights, and her husband writes for various pro-reform publications.
Others detained include a blogger known as the "Blogging Mullah," a cartoonist, a TV producer, the publisher of several newspapers, a disabled former newspaper editor and a business reporter.
Nakhle Elhage, news director at Dubai-based Al-Arabiya television network, said authorities told them their activities have been suspended until further notice but did not ask their resident correspondent Diaa al-Nasseri — an Iraqi — to leave.
Last Sunday, Al Arabiya in Tehran was told by the authorities to suspend their activities for one week.
RSF says that, even before the election, Iran held more journalists and cyber-dissidents in jails than any other country in the Middle East.
Hervieu said blogs, Twitter, YouTube and other Internet methods are the only way most people can convey information from the street. But the use of anonymity by blog posters trying to avoid repercussions makes information difficult to verify.
Many of those posting "are both spectators and activists," blurring lines of impartiality, he said.
He said small digital cameras passed from activist to activist and then to a foreign colleague or news organization are helping spread images, though their provenance is not always clear.
He noted the example of the much-viewed amateur video on YouTube, showing dozens of Iranians running down a street and shouting "Allahu Akbar" after police fired tear gas.
AP Executive Editor Kathleen Carroll said last week that, when controls are imposed, "we work with those restrictions, keeping in mind our ultimate goal is to be able to do our jobs as journalists," she said.
Reporters were also restricted during the 1979 Iranian Revolution, which saw the installation of the Islamic regime in power today.