In the streets around Abdel Munim Riyad square the atmosphere had changed. The air which had held a carnival-like vibe was now thick with teargas. Thousands of people were running out of nearby Tahrir Square and towards me. Several hundred regrouped; a few dozen protesters set about attacking an abandoned police truck, eventually tipping it over and setting it ablaze. Through the smoke, lines of riot police could be seen charging towards us from the south.