An Iranian activist, who recently invited former American embassy staff held hostage during the Islamic revolution to visit Tehran, has been beaten up by Islamic extremists.

Ebrahim Asghar-Zadeh, now a supporter of the reformist President Khatami, was attacked while addressing students at the University of Hamedan a town souhwest of Tehran on Sunday.

He was badly injured and taken to hospital.

Mr Asghar-Zadeh angered hardline conservatives when he issued the invitation for a reconciliation last month, on the 19th anniversary of the incident.