Mousawi has called off the protesters' rally for today after the Iranian Government and the police informed him that the Police in charge of crowd control would be carrying live rounds for their weapons.
Iran's defeated moderate candidate Mir Hossein Mousavi has cancelled a big rally, amid growing unrest over last week's presidential poll.
The government had declared planned protests against the re-election of President Mahmoud Ahmadinejad illegal.
Mr Mousavi called off the rally after being warned militias would be equiped with live rounds, the BBC understands.
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Can't stop the signal, Mal: