Egyptian authorities have arrested five people on allegations of vandalising a memorial erected at the site of the largest protest camp held last year by supporters of deposed president Mohamed Morsi, and forcibly dispersed by security forces, with hundreds killed.

Students of the nearby Al-Azhar University were among the dozens who marched on Thursday to the Rabaa Al-Adawiya Square and threw petrol bombs at the standing monument, which has been cloaked in sheets away from the public eye for monthss.

Five were arrested for harming the monument which, nevertheless, remained "perfectly intact," a security source told state news agency MENA on Thursday.

Featuring two brown arcs enclosing a large pearl-like ball, the memorial was built by the Egyptian military. Officials said the larger arc represents the army, the smaller one the police and the ball the Egyptian people..