German Chancellor Angela Merkel renewed calls for the release of Egypt's former president Mohamed Morsi, who has been held incommunicado since 3 July after being deposed by Egypt's army.

Merkel called for "an inclusive political process involving all groups of the Egyptian population," DPA reported. She gave her remarks in a press conference in the Germany capital, Berlin, on Friday.

The army said it has been protecting Morsi amid widespread instability.

Germany's calls come as protests in Egypt continue unabated with opponents and supporters of Morsi holding rival demos in separate parts of Cairo and other provincial towns on Friday.

Merkel highlighted that the anti-Morsi camp condemned being mistreated under the Islamist leader's rule, warning that doing the same with the other faction would stall Egypt's development process, DPA added.

The top United Nations human rights official also asked Egypt's interim government to explain the army's rationale behind Morsi's and his close aides' detention and whether it plans to put them on trial, a UN spokesman said on Friday.

Germany, Washington and the European Union have earlier urged an end to the secrecy imposed on Morsi's whereabouts, heaping pressure on the interim government to free the toppled president.

The German ministry spokesman said a "trusted institution" such as the International Committee of the Red Cross should be granted access to Morsi.

The US State Department condemned the detentions of Morsi and members of the Muslim Brotherhood as "politically motivated" and urged the military to free them.

Following Morsi's overthrow, several Brotherhood members have been detained over a range of charges including "inciting violence and thuggery."