Egypt's newly-formed National Coalition for Supporting Legitimacy, an umbrella group of 40 Islamist parties and groups led by the Muslim Brotherhood's Freedom and Justice Party, called on opposition leaders to condemn ongoing political violence and "break ties with corrupt figures" of the Mubarak regime.

"The coalition asserts that the [Egyptian] masses will not accept anything less than [democratic] legitimacy nor will they accept attempts to drag the country to chaos and reproduce the corrupt [Mubarak] regime, which Egyptians have risen against," reads the statement released by the coalition following mass demonstrations – estimated in hundreds of thousands - in support of president Morsi.

The coalition, formed a week ago, had announced it will continue its sit-in following Friday's demonstration, as the country braces for the widely-anticipated anti-Morsi rallies on 30 June – also expected to draw hundreds of thousands.

At least three were announced dead following intermittent clashes between Morsi's supporters and opponents since Wednesday in the governorates surrounding Cairo.

"The purpose of our sit-in is to reiterate the [president's] legitimacy which is the product of the people's free democratic choice, and to reject political violence," the statement continued.

President Mohamed Morsi narrowly won Egypt's first post-revolution presidential elections in June 2012 against Mubarak's last prime minister Ahmed Shafiq.

Sunday's protests, planned by organisers of a petition drive dubbed Rebel and backed by opposition – will take place on Morsi's first anniversary in power, demanding his resignation and snap presidential elections.

Campaigners accuse the Morsi administration of "failing to implement policies to improve the life of ordinary people."