Egyptian authorities have arrested more than 1 000 people, two rights groups said on Wednesday, in the wake of rare protests last week calling for the ouster of President Abdel Fattah al-Sisi.
The Egyptian Centre for Freedoms and Rights said 1 003 had been arrested, while the Egyptian Centre for Economic and Social Rights reported the figure of 1 298 detained.
Two prominent academics were also detained on Tuesday, a lawyer and a relative said.
Hazem Hosny, a Cairo University political science professor, was arrested on Tuesday night in front of his home, his lawyer Tarek al-Awadi said on his Facebook account.
French-educated Hosny was a spokesman for former Egyptian military chief of staff Sami Anan, who was detained after he attempted to run against Sisi in presidential elections last year.
The professor has been critical of Sisi on social media in recent days.
Hassan Nafaa, another prominent intellectual who teaches political science at Cairo University, was also detained from his home late Tuesday, family sources told AFP.
He too has denounced Sisi's heavy-handed approach in governing.
Nafaa told AFP earlier this week that Sisi's desired image as "Egypt's saviour from Muslim Brotherhood rule... has been completely dismantled".
In July 2013, Sisi led the military ouster of Muslim Brotherhood president Mohamed Morsi.
Demonstrations have effectively been banned since under an anti-protest law passed the same year.
Since last week, security presence has been stepped up around Cairo's iconic Tahrir Square - the epicentre of the 2011 uprising that toppled autocrat Hosni Mubarak - and other cities.
On Tuesday, AFP journalists saw police stopping and frisking people near Tahrir Square, and checking their mobile phones.
Last week's protests followed an appeal by Mohamed Aly, an exiled Egyptian businessman in Spain, to topple Sisi after accusing him of corruption.
Aly has called for fresh protests on Friday.
The growing list of arrests includes three journalists held for their coverage of the protests and award-winning human rights lawyer Mahienour El-Massry.
Egypt has also come under fire from rights groups for disrupting internet access to the popular app Facebook messenger and news sites such as the BBC.