'Uncertainty and apprehension' in Egypt's Tahrir Square
15 June 2012 Last updated at 13:24 BST
The Muslim Brotherhood has warned that Egypt's fragile democratic gains are under threat, after a surprise court ruling overturned last year's parliamentary elections.
Egypt could see "dangerous" days ahead if power is returned to those linked to the previous regime, it said.
The decision by the Supreme Court on Thursday has plunged the country into turmoil ahead of this weekend's presidential runoff vote.
The BBC's Lyse Doucet is in Cairo's Tahrir Square, and says there is "great uncertainty and a certain amount of apprehension" about what will happen next.