Human rights groups in Egypt have condemned a new law restricting public protests which has been signed by the interim President Adly Mansour.
The law bans protests without prior police notification.
Many believe the new legislation is aimed mainly at supporters of the now-banned Muslim Brotherhood and the ousted president, Mohammed Morsi.
Mass protests have led to the toppling of two Egyptian presidents in the past three years.
The law was signed as more protests took place in several cities on Sunday.
Thousands of supporters of deposed President Mohammed Morsi gathered in Cairo and elsewhere.
They were marking 100 days since security forces broke up sit-ins calling for his reinstatement - violence which saw hundreds killed.
A similar protest on Friday in Cairo led to clashes with anti-Morsi demonstrators and police.
Mr Morsi, who has roots in political Islam, is currently on trial alongside other leading members of the Muslim Brotherhood on charges including incitement to the killing of protesters in 2012.
Human rights groups in Egypt rejected the draft law before it was enacted by interim President Mansour.
"The draft law seeks to criminalise all forms of peaceful assembly, including demonstrations and public meetings, and gives the state free hand to disperse peaceful gatherings by use of force," 19 Egyptian organisations said in a statement.
But Prime Minister Hazem Beblawi, speaking to the AFP news agency, said the new law was designed to protect "the right of protesters" and required them to give "notice" rather than seek permission.
Government sources were quoted as saying the legislation had been watered down to require three rather than seven days' notice.
Parliamentary and presidential elections are due to take place next year, but human rights groups have accused the military-backed authorities of anti-democratic tendencies.
Thousands of Muslim Brotherhood members have been detained since Mr Morsi's overthrow, though the authorities say this is part of combating "terrorism".