Plainclothes supporters of Egypt's President Hosni Mubarak beat up activists protesting against a referendum yesterday on a new presidential election system that allows opposition candidates but sets them high hurdles.

Police arrested 46 members of opposition groups, over half of them in the Suez Canal town of Ismailia, including local party leaders who marched to back a referendum boycott, police sources said.

In Cairo, riot police penned in dozens of members of the Kefaya (Enough) protest movement while men in plain clothes dragged some away by force, hitting them as they went.

The men, summoned by police, pushed to the ground Mohamed Abdel Qaddous, a prominent journalist and member of the Muslim Brotherhood opposition movement, then kicked and punched him, witnesses said.

An alliance of six civil society groups said in a statement: "The thugs beat a group of demonstrators within sight of the policemen, who stood watching."