Supporters of Iran's defeated presidential candidate Mir Hossein Mousavi have rallied in northern Tehran, witnesses told the BBC.
A BBC correspondent in Tehran said one eyewitness told him the rally was even bigger than Monday's demonstration by hundreds of thousands of opposition supporters.
Supporters of President Ahmadinejad have also rallied in the city, but according to pictures on state television, the demonstration did not appear to have been on the same scale as the opposition gathering.
Strict controls have been imposed on the activities of all foreign media organisations trying to gather news on the streets.
But there are no controls on what our correspondent in Tehran, Jon Leyne, can say.
The coming days are likely to be crucial in determining which direction the protests are going to take.
The BBC's Max Pearson spoke to a woman in Tehran who did not want her name to be used.
First broadcast 16 June 2009
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