Egyptian protesters loyal to deposed president Mohamed Morsi called for a "million person march" on Tuesday against his ouster.
They also called on demonstrators to march to "security administration buildings" throughout Egypt on Monday night to protest the deaths of 72 people at a Saturday rally.
"We... call for a million person march under the banner of 'Martyrs of the Coup' on Tuesday," the Anti-Coup Alliance of Islamist groups organising the protests said in a statement.
The group urged Egyptians "to go out into the streets and squares, to regain their freedom and dignity -- that are being usurped by the bloody coup -- and for the rights of the martyrs assassinated by its bullets."
It also called for protesters to march to security buildings in provinces across Egypt on Monday night "to condemn the criminal acts and the firing of live ammunition by the interior ministry at peaceful demonstrators."
The protest calls comes after at least 72 people were killed at a sit-in in support of Morsi on Saturday morning.
His loyalists accused security forces of using live fire against unarmed protesters but Egypt's interior ministry said only tear gas was used.
Egypt's polarisation has been growing since Morsi's July 3 ouster by the army after massive protests against him.
His supporters remain defiant, insisting he will be reinstated, but the interim government has said it will move to disperse the protests and warned it would take "decisive" action if demonstrators overstepped their bounds.