Egypt's Muslim Brotherhood is calling for mass rallies Friday, after the military-backed government released deposed President Hosni Mubarak from prison.
Mr. Mubarak, an ex-military commander who ruled Egypt for 29 years, was transferred Thursday to a military hospital near Cairo, where he will remain under house arrest.
The 85-year-old is awaiting trial for murder in connection with the killing of hundreds of protesters during a popular uprising that forced him from power in 2011. He has also been charged with corruption.
An Egyptian court ordered Mr. Mubarak's release this week, ruling his pre-verdict detention had exceeded legal limits.
The ruling has angered the Muslim Brotherhood, whose democratically elected leader, Mohamed Morsi, was forced from power by the military last month and remains in prison.
The Brotherhood and the so-called "Anti-Coup Alliance" have called for a "Martyr's Friday" of mass demonstrations against the military, raising fears of fresh violence.