Iran has escalated its repression of domestic media while simultaneously trying to muzzle scores of Iranian journalists working abroad. The campaign of smears and intimidation comes as the regime - under mounting western pressure to curb its nuclear programme - gears up for presidential elections in June.
More than a dozen mostly reformist journalists were detained in raids on the offices of at least four newspapers on Sunday, accused of co-operating with "anti-revolutionary" Persian-language media organisations based overseas. Such arrests in Iran are nothing new, but sweeps against media on this scale are rare.
The crackdown went beyond targeting reformist news organisations. A popular conservative news website, Tabnak, was blocked at the weekend. And among those arrested was a correspondent for Iran's labour news agency, which has reported on layoffs in the country's factories.
Security officials have also intensified the harassment of families in Iran of exiled journalists, in some cases arresting, interrogating and threatening their relatives.
One British-based Iranian journalist said: "They summoned my elderly mother recently and warned her that unless I returned to Iran they'd stop her pension and ruin her life. No matter how far you are from Iran, you're never safe."
The regime is also using a new tactic. Its cyber-activists have set up fake Facebook accounts and blogs in the names of Iranians working for the BBC's Persian service in London. In these, the supposed journalists damn themselves, mostly by admitting to leading sexually promiscuous lifestyles in England or working for MI6. The fabrications are then recycled by Iranian state media in an attempt to discredit BBC Persian's presenters and reporters.
Sadeq Saba, the head of BBC Persian, has himself been a victim of this "identity theft". A fake blog, created in his name and designed to look like his BBC diary, claims that the corporation's task is not to report news but to make it up.
"They published fake interviews with me where fake journalists ask me fake questions and I give fake answers," Mr Saba said.
BBC Persian is reviled by authorities because of its popularity - with its television channel, radio station and website used by an estimated 12 million Iranians.
"They don't like people having access to independent and alternative sources of news," Mr Saba said.
Iran regards the BBC as a servant of the British government, a "little Satan" that pulls the strings of the "Great Satan", America.
The Iranian regime has accused the BBC of helping to foment the huge street protests against president Mahmoud Ahmadinejad's disputed re-election in 2009.
BBC Persian accepts it played a role during that tumultuous period - but only by accurately informing Iranians of what was happening. The corporation denies Iranian allegations that it tried to recruit Iranians for "espionage and psychological warfare".
Iranian journalists at Radio Farda, the Persian service of Radio Free Europe/Radio Liberty, which is funded by the US Congress, have also been targeted. The relatives in Iran of at least 20 Radio Farda staff members have been threatened and detained.
Some state-controlled Iranian media have joined in bashing their colleagues abroad, branding them "the media soldiers of the West".
Many Iranian journalists fled their homeland after the crackdown on reformist and independent media in recent years.
From London, Toronto and New York - using their extensive contacts in Iran - they provide a balanced coverage of events inside Iran. This includes reporting on human-rights abuses and other subjects that are off limits to journalists in the country.
But, like BBC Persian, most also showcase the best of Iran, covering its vibrant and celebrated cinema and art scene.
Mr Saba insisted the threats against his staff and their families would in no way influence BBC Persian's reporting on Iran: "We are committed to impartial and fair coverage of Iran whatever the Iranian government does."
While the BBC is not allowed to have an office in Tehran, the channel does its best to include the Iranian government's views in its coverage, he said.
The smear campaign against BBC Persian has not passed unchallenged in Tehran. A conservative website, Baztab, last week criticised the spread of hoax material, saying the tactic would backfire.
Peter Horrocks, director of BBC Global News, said the head of Iran's national news agency acknowledged on the sidelines of a recent conference in Moscow that it was "un-Islamic" to target the families of journalists living abroad.
So while the intimidation of overseas Iranian journalists continues, Mr Horrocks added in a report this weekend, there is clearly a "debate in the regime" as to whether such action is justified.