BELGRADE, Serbia-Serb opposition is blocking the parliamentary ratification of a pre-membership deal with the European Union over the arrest of war crimes suspect Radovan Karadzic.

Lawmakers of the Serbian Radical Party are telling the Serbian parliament they will prevent a vote on the deal until authorities explain how one of its supporters died from injuries sustained in clashes with police during a rally in July against the arrest of the Bosnian Serb wartime political leader.

Serbian Radical Party deputy president Tomislav Nikolic said Tuesday that Karadzic was illegally arrested in July. He has demanded that authorities reveal who was responsible for the death of the protester.