The National Coalition for Supporting Legitimacy, which supports former President Mohamed Mursi, called on Egyptians to take part in planned demonstrations on Friday.
According to the coalition, the demonstrations, which are held under the title of "Bless the youth... the revolution's backbone", are set to continue for one week in governorates all over Egypt.
In a statement addressing Egyptian youths, the Islamist alliance said, "Continue your revolution as you hold high the banner of pride for the entire people of Egypt."
Allies of the former president have been staging demonstrations to protest what they called a military coup that toppled Mursi and removed him from power.
The alliance had called for demonstrations last Friday under the title "The youth are the revolution's backbone".