About 400 members of the April 6 Youth Movement gathered for a protest at dawn against what they called severe policies being used by Egypt's Interior Ministry against protesters and political activists, Ahram Online reported. The protest took place outside Egyptian Interior Minister Mohamed Ibrahim's home.
Police dispersed the crowd by firing teargas. Dozens of people suffered from asphyxiation due to the teargas.
Four protesters were arrested for calling the Interior Ministry a "prostitute" and waving underwear in the air.
April 6 Youth Movement's Democratic Front released a statement Friday denouncing alleged police brutality.
"Such violence and abuse from police will never pass unnoticed," the statement said. "Any bloodshed [of our members] will lead to an outrage that neither the interior ministry nor the regime has seen before."
The violence came after 53 activists were arrested Wednesday in Tahrir Square for erecting barriers and obstructing traffic.