"It is clear that the Iranian government fears its own people."
White House spokesperson Robert Gibbs meanwhile said that the web giant, Google, and other internet service providers had been "unplugged" in Iran.
Reporters Without Borders says the blocking of Google's Gmail e-mail system takes the drive to control cyber-space to a new stage.
But the organisation claims that most Iranian internet users know how to sidestep censorship and access blocked websites.
Correspondents say a number of governments - notably China and Burma, as well as Iran - make strenuous efforts to block modern internet communications among their opponents.
'Accurate and impartial'
The BBC, Deutsche Welle and Voice of America said the Iranian authorities' jamming was affecting services on the Hotbird satellite, which covers audiences across Europe and the Middle East.
President Mahmoud Ahmadinejad told a rally Iran was now a "nuclear state"
These include BBC Persian Television, the Voice of America Television Channel in Persian and Radio Farda; and Deutsche Welle's Television and Radio services. BBC World News - the English-language channel - was also jammed.
"We condemn any jamming of these channels. It contravenes international agreements and is interfering with the free and open flow of international transmissions that are protected by international treaties," the broadcasters said in a joint statement.
"The Iranian authorities are using the same satellite services to broadcast freely around the world including broadcasts in English and Arabic; at the same time they are denying their own people programmes coming from the same satellites from the rest of the world," they added.
Footage said to show a policeman beating a protester
On Thursday, a day-long security clampdown in the Iranian capital Tehran succeeded in preventing large-scale opposition protests as the nation commemorated the Islamic Revolution.
The opposition turnout was dwarfed by huge crowds at the state-run celebrations in the centre of Tehran.
President Mahmoud Ahmadinejad addressed the rally, saying Iran was now a "nuclear state" and had produced its first stock of 20% enriched uranium.
But the White House said the assertion was based more on politics than science.
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