Amateur footage believed to show opposition supporters demonstrating amid the Islamic Revolution anniversary celebrations in Iran, has been posted on YouTube.
The protesters, some carrying a green flag, chant "Ya Hossein, Mir Hossein" in support of opposition leader Mir Hossein Mousavi.
The protesters are thought to be near Saddeqiya Square in Tehran, which is where opposition leader Mehdi Karroubi was attacked earlier in the day.
Opposition leader Mehdi Karroubi had been intending to attend the Saddeqiya street rally, reports say, but his bodyguards were attacked by members of the government's Basij militia as he emerged from his car.
This video has not been verified by the BBC.