Ahram Online captured the moment police fired teargas on a peaceful demonstration in Talaat Harb Square in Downtown Cairo.
Earlier in the day, other demonstrations in the capital were dispersed by police who used water cannon, tear gas and arrested dozens of activists.
The crackdown comes just two days after a controversial protest law was passed, regulating the way in which demonstrations can be legally held in Egypt.
The new law states that protesters must inform the police ahead of the protest - it is understood that this did not happen in this case.
The law also states that police must first ask participants to "voluntarily leave the demonstration through several audible verbal warnings". Ahram Online's reporter at the scene heard no such warnings before the security forces fired tear gas.
Video by Simon Hanna