UN Secretary-General Ban Ki-Moon stressed the importance of peaceful protests in Egypt, expressing concern over deadly clashes that took place in Cairo Friday with mass protests anticipated two days later.

"Ahead of announced demonstrations marking a national holiday in Egypt on Sunday, the Secretary-General stresses the importance of peaceful protest, respect for freedom of assembly and commitment to non-violence. He also expresses his concern at the serious violence today in Cairo," reads a statement issued on the UN's website on Friday.

The Muslim Brotherhood, from which Egypt's deposed president Mohamed Morsi hails, and its Islamist allies are planning to head to Tahrir Square on Sunday to once again call for his reinstatement and reverse what they describe as a military coup.

On Friday, protests were held by loyalists of Morsi in Cairo but failed to reach key locations, including Tahrir Square and the presidential palace amid stiff opposition from security forces and local residents.

One protester was killed in clashes between supporters of Morsi and local residents in Manial in central Cairo. Other confrontations also erupted later between supporters and opponents of Morsi in Ibn Sandr Square in the suburb of Zeitoun, western Cairo, leaving three more dead.

"He [Ban Ki-Moon] also expresses his concern at the serious violence today in Cairo,” the UN statement added.

"The Secretary-General continues to underscore the need for political inclusion, full respect for human rights, including of those detained in prison, and the rule of law as the basis for a peaceful, democratic transition."

"These are principles to which the Egyptian authorities themselves have committed in the roadmap they have set forth."

After fresh talks with EU envoy Catherine Ashton, Egyptian officials have said they are not committed to an inclusive approach to negotiations with the Muslim Brotherhood until protests are halted, according to European diplomats.