Mohamed Mahmoud Street, which runs east from Tahrir Square toward the Interior Ministry headquarters in central Cairo, has become the focal point of street fights between protesters and the black-clad Central Security Forces.
For three days, protesters have been carried or driven back from the front line by comrades after coming under fire from rubber bullets and what they believe is either particularly potent or poisoned tear gas.
At least 33 people have died across the country, according to the Health Ministry, many from tear gas asphyxiation. Doctors also believe that security forces have fired live ammunition.
Al Jazeera's Mike Hanna reports from Cairo.