Egypt has ordered the arrest of two leading activists for defying a new law on demonstrations, as it widened a crackdown against backers of ousted president Mohamed Morsi.
The suppression of mainly secular youths is seen as the opening of a new front by the military-installed authorities, which justified the toppling of Morsi by saying it was responding to massive demonstrations against his rule.
Morsi's overthrow on July 3 has been followed by a massive crackdown against his Islamist supporters, with more than 1000 people killed and thousands arrested.
On Wednesday, the general prosecutor ordered the arrest of Ahmed Maher, founder of the April 6 movement that spearheaded the 2011 revolt against former president Hosni Mubarak, and Alaa Abdel Fattah, a prominent activist, state news agency MENA said.
"The two are accused of inciting protesters to hold demonstrations that broke the protest law," the prosecution said, referring to Tuesday's demonstrations held in Cairo in defiance of the new law that requires organisers to seek prior permission for protests.
The report added that 24 other protesters who joined the demonstration had been ordered detained for four days.
The protests were broken up by police using water cannon and tear gas, in the first use in Cairo of the greater powers given to them under the new law.
Judiciary and other sources said about 60 protesters were detained, including prominent activist Mona Seif, founder of a campaign against military trials of civilians.
Seif and a group of 15 other women and 12 men were later released in the middle of the night on a desert road some 10km south of Cairo.
"The ministry of interior alleges that each one of us had been dropped at her house, which means that all of us are living in the desert," Seif wrote later on Twitter.
On Wednesday, police used tear gas to break up a demonstration against the law in second city Alexandria, as protesters pelted them with stones.
Egypt's cabinet was in a meeting Wednesday to discuss the latest developments and the implementation of the protest law, state media said.
Under the law, protesters can be jailed for up to five years if found guilty of offences ranging from covering their faces to carrying weapons at demonstrations.