The alleged assault o­n two reformasi ISA detainees by camp guards requires urgent and immediate independent inquiry, an United Nations official said today.

"Custodial assaults of detainees by security officials are matter of grave concern," Param Cumaraswamy, UN special rapporteur o­n the independence of judges and lawyers said in a statement.

The two men - Tian Chua, vice-president of the opposition Keadilan and Hishamudin Rais, a social activist - have been held since April 2001 at Kemunting detention centre in Perak under the tough Internal Security Act (ISA).