Ten members of the panel drafting Egypt's new constitution have suspended work after authorities arrested protesters and fired warning shots, water cannons and tear gas at Cairo rallies.
Egyptian police arrested and detained more than 70 protesters among dozens who were demonstrating in Cairo against an article in the revised basic law that allows the military to try civilians in certain cases, a security official said on Tuesday.
Hoda El-Sadda, a senior member of the panel, said that she and nine others had suspended work on Tuesday after the arrest of protesters, including leading activists.
Police arrested the protesters because the demonstration was not authorised, officials said, referring to a controversial new protest law enacted over the weekend which requires protest organisers to give three days written notice to authorities.
Al Jazeera's Gregg Carlstrom, reporting from Cairo, said on Tuesday that some of the protesters tried to regroup in downtown Cairo, by Talaat Harb square, where police used water-cannon and tear-gas on them again.
"The interior ministry says the protesters threw rocks at the police," Carlstrom said.
Carlstrom and another Al Jazeera correspondent reported that interim Prime Minister Hazem El Beblawi was meeting political figures and activists to try to contain the situation on Monday night.
But Carlstrom's colleague said: "Protesters will not leave until detainees released."
Among the 74 people arrested were Mona Seif, founder of a campaign against military trials of civilians, and Ahmad Harara, a dentist who lost his eyes to birdshot during protests against Hosni Mubarak in 2011 and against the military junta that ruled Egypt immediately after Mubarak's fall.
In Tuesday's first protest, about 100 largely secular activists rallied in the streets to commemorate an activist, Gaber Salah, known by the nickname "Gika" - killed by police a year ago.
Police quickly deployed, and an officer told the gathering they had no permit, activists said.
Hours later, protesters demonstrated in front of the Shura Council on Tuesday, where the constitution panel sits, when police used water canon to disperse them and later made arrests.
Mohamed Salmawy, the spokesman of the constituent assembly, said earlier on Tuesday that a referendum on Egypt's amended constitution would be held in December, in an important step towards elections.
"The referendum will be held before the end of the month," Salmawy said.
That contradicted comments made by Beblawi on Sunday when he said that the referendum would be held in the second half of January.
Security forces had heavily deployed across town where Morsi supporters had planned to hold a rally later on Tuesday.