At least 20,000 protesters take over Qasr al-Nil Bridge, connecting Giza to Tahrir Square in downtown Cario.
Police fired hundreds of tear gas canisters which protesters picked up and threw them back at police and into the Nile.
Crowds cheered and sang the Tunisian national anthem, drawing inspiration from the popular Tunisian uprising that ousted former President Zine al-Abidine Ben Ali earlier this month.
Some armored vehicles drove into crowds of protesters, appearing to run them over.
Earlier police fired the noxious tear gas on thousands of protesters in the Dokki neighborhood.
Plumes of smoke could be seen all the way from Downtown Cairo.
Smoke also filled the area behind the Egyptian Museum in Tahrir Square, reportedly coming from a police car on fire.
Tahrir was cordoned off by security forces earlier in the day. A small group of protesters ran through the downtown square despite the heavy security presence there.
