An Egyptian rights lawyer says prosecutors have ordered the brother of a U.S.-based well-known Egyptian activist to remain in custody pending an investigation into taking part in activities of an outlawed group and disseminating fake news.

Wael Ghonim, who led a Facebook page that helped ignite the 2011 pro-democracy uprising, has said security forces arrested his brother Hazem Thursday.

Lawyer Mohammed el-Baker tells The Associated Press Sunday that prosecutors ordered Hazim Ghonim to remain in custody for 15 days.

FILE - In this Feb. 8, 2011 file photo, Egyptian Wael Ghonim, center, talks to the crowd in Tahrir Square, in Cairo, Egypt. Ghonim said late Thursday, Sept. 19, 2019 in a video on his twitter account that authorities raided his parents' house in Cairo and arrested his brother Hazem, whom he described as "a political person" and confiscated his parents' passports. Ghonim alleges that the Egyptian embassy in the U.S. threatened him the previous day "something will happen" if he didn't stop criticizing Egypt's government on social media.  (AP PhotoTara Todras-Whitehill, File)

FILE - In this Feb. 8, 2011 file photo, Egyptian Wael Ghonim, center, talks to the crowd in Tahrir Square, in Cairo, Egypt. Ghonim said late Thursday, Sept. 19, 2019 in a video on his twitter account that authorities raided his parents' house in Cairo and arrested his brother Hazem, whom he described as "a political person" and confiscated his parents' passports. Ghonim alleges that the Egyptian embassy in the U.S. threatened him the previous day "something will happen" if he didn't stop criticizing Egypt's government on social media. (AP PhotoTara Todras-Whitehill, File)

Wael Ghonim claimed that his recent criticism of President Abdel-Fattah el-Sissi prompted authorities to retaliate by detaining his brother.

The arrest came as Egyptian social media was awash with calls for anti-government protests last week. On Friday, hundreds joined in scattered, small protests in Cairo and other cities.