Egypt's prime minister has described the latest protests in the capital Cairo as a "counter-revolution".
Kamal al-Ganzouri said those taking part in the deadly clashes were "not the youth of the revolution", a reference to the uprising in February that toppled President Mubarak.
His comments came as violence continued for a second day, following the deaths of eight protesters on Friday.
The demonstrators want an immediate handover to civilian rule in Egypt.
They object to the appointment of Mr Ganzouri last month by the ruling military.
The prime minister - who previously served under Mr Mubarak but has since distanced himself from the former regime - said the security forces had responded to the violence with patience.
"I said and I am still reiterating that we will never confront any peaceful demonstrations with any kind of violence, even the verbal kind," he said. "I am committed to this."
Saturday's protests began at dawn when protesters clashed with the security forces near parliament.
The demonstrators threw stones at riot police who had sealed off the streets around the building with barbed wire.
The protesters also set fire to government offices.
Security forces responded with water cannon and some threw objects at the protesters from the tops of buildings.
The activists have been staging a sit-in in the centre of Cairo since Mr Ganzouri's appointment, which followed mass protests last month in which nearly 40 people were killed.
On Friday, the security forces stormed a protest camp to try to move the activists away.
Although the troops later pulled back, street battles continued for much of the day.
Egyptian state television said eight people had been killed and about 300 injured.
Egypt's military council took control of the country in February after President Hosni Mubarak was forced from power by popular protests.
The military has promised a transition to civilian rule, with presidential elections due in June 2012.
Parliamentary elections are taking place in several stages.
The second round of voting on 14 and 15 December saw people go to the polls in nine of the country's 27 provinces.
Preliminary results suggest that Islamist parties have consolidated their lead over their liberal and secular rivals.
After the voting process is completed next month, the new lower house of parliament will appoint a 100-member committee to draw up a new constitution.
The protesters have accused the military of trying to entrench its position under the terms it has set out for the drafting of the constitution.