opposition announced a third day of street demonstrations Wednesday as the country's most powerful military force warned of a crackdown against online media in its first pronouncement on the deepening election crisis.
Blogs and websites such as Facebook and Twitter have been vital conduits for Iranians to inform the world about protests over Friday's disputed election.
The web became more essential after the government barred foreign media Tuesday from leaving their offices to report on demonstrations on the streets of Tehran.
The Revolutionary Guard, an elite military force answering to Supreme Leader Ayatollah Ali Khamenei, said through the state news service that Iranian websites and bloggers must remove any materials that "create tension" or face legal action.
The Guards are a separate military with enormous domestic influence and control of Iran's most important defense programs. They are one of the key sources of power for a cleric-led establishment that has been pushed by the crisis into an extraordinary public defense of the Islamic ruling system.
The supreme leader made a highly unusual appeal Tuesday in response to tensions, telling Iranians that all citizens should hold fast to their belief in the system despite disagreements over the election.
Despite official warnings and a ban on street demonstrations, some websites allied with opposition leader Mousavi said Wednesday that supporters should gather in a downtown square in the late afternoon.
The announcement raised the prospect of further clashes with security forces. The violence has left at least seven people dead, according to Iran's state media.