Prosecutors summoned Shady el-Ghazaly Harb for an investigation into accusations of disseminating false news and insulting the president, among other charges, his wife Fatima told The Associated Press on Tuesday.
The prosecutors set his bail at 50,000 Egyptian pounds, or about $2,810, late Monday. It has been paid but authorities have refused to let him return home, she said.
Rights lawyer Doaa Moustafa said prosecutors have ordered Harb held for 15 days pending investigation, and that he also faces charges of joining an outlawed group. He has been added to a case that involves another activist, Amal Fathy, and a young comedian, Shady Abu Zaid, both of whom are also detained.
Shady el-Ghazaly Harb was one of the young leaders behind the 2011 uprising that toppled President Hosni Mubarak.
Freedoms won during the uprising have rapidly eroded since el-Sissi led the military overthrow of President Mohammed Morsi, an Islamist who was freely elected but proved divisive, in 2013.
Since then, authorities have waged a wide-scale crackdown on dissent, jailing thousands of people, mainly Islamists but also several prominent secular activists, including many of those behind the 2011 uprising. The government has banned unauthorized protests and blocked hundreds of websites, including many operated by independent journalists and rights groups.
The government has defended such measures, saying it is trying to restore stability, revive the economy and defeat an Islamic State-led insurgency based in the Sinai Peninsula.
Also on Tuesday, an Egyptian court handed out sentences - ranging from five to ten years - to five defendants in prison on terror-related charges that include killing a Coptic Christian in 2010. The Cairo Criminal Court said the defendants had set up a militant group that aimed to attack security personnel, tourists and the country's Christian minority.
Egypt has been battling Islamic militants for years, but the insurgency gained strength after Morsi's overthrow. The militants have focused their attacks on security forces and Christians.
In February, Egypt launched a massive security operation against militants in Sinai as well as parts of Egypt's Nile Delta and the Western Desert, along the porous border with Libya.
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