Several dozen protestors have gathered outside the Department of Foreign Affairs in Dublin calling for the release of four Irish citizens.
Three sisters in their 20s and their 17-year-old brother from the Halawa family have been in custody in Cairo since Saturday.
It is still unclear whether Irish embassy officials have yet been given access to the siblings.
Meanwhile the supreme leader of Egypt's Muslim Brotherhood has been arrested on charges of inciting the murder of protesters.
Mohamed Badie's detention comes as authorities continue a crackdown on the party of ousted president Mohamed Morsi.
The action has sparked deadly protests across the country, during which almost 900 people have died.