Egyptian authorities have released over 100 people who were detained in rare protests across the country last month, rights lawyers said on Saturday.

Lawyers Mustafa el-Demiry and Khaled Ali told AP news agency that the detainees were released late Friday pending investigation into claims that they took part in the activities of a banned group and disseminating false news on social media platforms.

Civil society groups report more than 2,000 people were detained in the 20 September protests, which prompted the UN High Commissioner for Human Rights, Michelle Bachelet, to express concern about reports of lack of due process.

Egypt slammed the statement saying it was "based on baseless information since the allegations it contains are based on false assumptions".

The anti-government protests were met with counter pro-government demonstrations, as President Abdel Fattah el-Sisi's supporters took to the streets to show their trust in the leader.

President el-Sisi is Egypt's sixth president, and has served since 2014.