Former presidential candidate Bothaina Kamel was allegedly attacked on Sunday by a group of men she described as Muslim Brotherhood supporters, she told Aswat Masriya.
Kamel says the windows of her car were smashed before she was physically assaulted by a group of bearded men, some of whom carried the yellow Rabaa flags used by supporters of ousted president Mohamed Morsi since the violent dispersal of their sit-in on 14 August.
The attack happened when she was passing through Giza's Dokki district, a site of previous clashes.
Kamel has been an active opponent of Morsi and the Muslim Brotherhood. She also opposed military rule following the ouster of Hosni Mubarak in 2011 and ran in the 2012 presidential elections.
Rallies took a violent turn in Dokki on Sunday, where police fired rounds of teargas after local residents clashed during pro-Morsi protests heading towards Tahrir Square, eyewitnesses and Ahram Online reporters said.
Clashes also broke out in several other locations across Egypt on the 40th anniversary of the 6 October War of 1973. The military planned celebrations while Morsi supporters called for fresh rallies.
On Friday, former spokesman of the National Salvation Front (NSF) and current spokesman of the Constitution Party, Khaled Dawoud, was stabbed by Morsi supporters in the chest and wrists.
He said he was attacked by protesters supporting Morsi while driving his car down Qasr El-Aini Street in front of Abou Al-Rish Bridge.
Egypt has been gripped by prolonged violence since the military overthrow of Morsi on 3 July after mass demonstrations against his turbulent year in office.
The ouster of the former president enraged Islamists, who have denounced the move as a violation of democratic "legitimacy."
Militants elsewhere have taken up arms against the state. The army has been battling an insurgency in Sinai, adjoining Israel and the Palestinian Gaza Strip, where they allege Islamist militants have mounted almost daily attacks on security and army targets, killing dozens.