Protesters have gathered on the streets of Egypt's capital Cairo, amid calls for more rallies over the deaths of 74 fans at a football match on Wednesday.
Sporadic clashes have already been reported in the city, and large rallies are expected after Friday prayers.
Hundreds were injured in fighting between security forces and protesters across the country on Thursday.
Many Egyptians blame the police for causing the football riot, in the northern city of Port Said.
Most of the dead were believed to be supporters of Cairo's al-Ahly team, who were attacked after losing a match to Port Said side al-Masry.
A group of hard-core al-Ahly fans known as the "ultras" have accused the authorities of allowing the killings to happen.
They say the authorities wanted revenge because the ultras were among those battling the police during last year's revolution that ousted strongman ruler Hosni Mubarak.
Anger over the deaths has combined with widespread frustration at the pace of reforms undertaken by the interim military rulers.
Early on Friday protesters and security forces clashed outside the interior ministry, which is seen by protesters as an unreformed institution dominated by Mr Mubarak's supporters.
A doctor at the scene told the Associated Press that one person had been killed.
Protester Wael Nawara told the BBC's Network Africa programme that many middle-ranking officers loyal to the former president were still in charge at the ministry and were "conspiring against revolution".
"There have been many calls throughout the last few months of restructuring the ministry of interior to bring the officers who are responsible for earlier deaths to trial, but nothing really has changed much in the behaviour of the ministry," he said.
The BBC's Yolande Knell in Cairo says protesters have spent the night dismantling concrete security walls that were erected around the ministry after a previous outbreak of unrest late last year.
Protesters are planning several marches across the city later, and there will be special funeral prayers at Tahrir Square for those who died at the football match.
Thousands gathered outside the ministry on Thursday and became embroiled in angry clashes with security forces. Officers used tear gas to disperse the crowds.
The health ministry said more than 1,000 protesters were injured, some with broken bones, most suffering from tear gas inhalation. Some 54 police officers and soldiers were also reported injured.
The unrest has now spread across the country, and two people were shot dead in Suez as a crowd of hundreds attempted to overrun a police station.
The government has dismissed several senior officials in response to the football deaths.
Port Said's director of security and the head of investigations were suspended and are now in custody.