I just found this courageous Iranian blogger who has filmed parts of the International Women's Day demonstration in Tehran on March 8th, 06
You can see the videos of the incident here, here, there and there
You can clearly see the security forces attacking the crowd and you can also hear the women singing in defiance (women singing is banned in Islam).
Then women start calling them Savage, Savage, Savage! and Police charge at the crowd and beat them up more!
It is said that many were arrested and dozens were also injured.
Update 1: Rooz Online reports: Iranian Police Violent Crackdown on International Women Day