Unidentified assailants attacked protestors in Tahrir Square at midnight, Monday, after thousands gathered to demonstrate against Egypt's election results, that will see Mubarak's last prime minister Ahmed Shafiq and the Muslim Brotherhood's Mohamed Morsi face each in a runoff vote on 16 and 17 June.
Two hours earlier, unknown individuals ransacked and set fire to the former regime member's presidential campaign headquarters in Dokki, Cairo. Security forces arrested those suspected of starting the blaze. Fire trucks brought the fire under control a short while later.
During Monday afternoon, hundreds had staged protests against the electoral outcome outside Egypt's Supreme Constitutional Court (SCC), and the headquarters of Egypt's Supreme Presidential Electoral Commission (SPEC) before joining Tahrir Square in the evening.
Similar protests took place across the country, including in Egypt's coastal city of Alexandria.
"We are sending a message to the Supreme Council of Armed Forces (SCAF) that we will never accept Ahmed Shafiq as our next president. He is the second Mubarak and was even in the Air Force like the ousted leader," says Aly, 24, a pharmacist who often works with the makeshift field hospitals during the clashes. "Personally I think the elections were rigged to put Morsi first, as it would have been a crisis if Shafiq was top – but, make no mistake, Shafiq is the military's man."
As the numbers grew to thousands, protesters– led by Khaled Ali, a former presidential contender and a left-wing labour lawyer – marched to Talaat Harb Square and around downtown Cairo before returning to Tahrir.
"Smash Shafiq on his head," the marchers chanted, whilst holding the former prime minister's presidential campaign posters upside down with his face crossed out.
Others chanted "Down with the dogs of the military regime" and called on bystanders on balconies overlooking Talaat Harb street to join them.
One protestor held a poster saying "If Shafiq wins, we are all dead" and others had the Ultras football fan flags of Zamalek White Knights team.
At one point protesters considered attempting to take down a huge billboard of Shafiq's campaign overlooking 6 October Bridge.
As traffic came to a standstill on the downtown streets, drivers abandoned their cars. There was mixed reaction from onlookers. One female shopper called out "Why are you angry now? Look what you've done –you've ruined everything."
Whereas another, an older male taxi driver told a group of people in the march, "God bless you, young people, I would join you if I didn't have to work."
Many protesters were angry with the possible return of Mubarak's last prime minister to power, and also what they believed to be vote-rigging against Nasserist candidate Hamdeen Sabbahi, who finished third in the poll.
"The election was rigged by the SPEC to preserve the old regime," Khaled Ali told Al Jazeera Mubasher TV.
"I am calling for an independent judicial commission to review all ballots in order to confirm that the vote was rigged for Shafiq," Ali added.
Many of the protestors who stayed on Tahrir until the early hours of Tuesday morning, agreed with Ali.
"The elections were clearly controlled by the state," said Alaa Shafani,45, a ceramic worker from Mansoura whose son lost his leg during clashes with the police last year. "I boycotted the elections in the first place because they are illegal, how can you have presidential elections without a constitution?"
In the afternoon, outside SCC and SPEC headquarters, protestors had demanded the enforcement of a 'disenfranchisement law' banning former regime figures like Shafiq from returning to political life.
Application of the law – which has been endorsed by Parliament and the military junta but which still awaits approval by the SCC – would exclude Mubarak's last prime minister, Ahmed Shafiq, from the presidential race. Liberal groups, for their part, are lobbying for Nasserist presidential contender Sabbahi to replace Shafiq in the upcoming runoffs.
Demonstrators called on Morsi to ally with other presidential contenders – such Abdel-Moneim Abul-Fotouh and Sabbahi – to unite against 'remnants' of the Mubarak regime, in a reference to Shafiq.
Groups that endorsed Monday's demonstration outside the SCC and SPEC headquarters included the Revolutionary Youth Coalition, the Kefaya protest movement, the April 6 Youth Movement and the Revolutionary Socialists.
The SPEC announced at a Monday press conference that the Muslim Brotherhood's Morsi and Mubarak-era minister Shafiq would face each other in next month's runoff poll.
According to the constitutional declaration, issued by the ruling military council following last year's 18-day uprising and approved via popular referendum, decisions made by the SPEC cannot be appealed.
Runoffs for the presidential elections are slated for 16 and 17 of June.