The party said in a statement the murders were not just an attempt to obstruct the trial of those accused for the March 2003 assassination of Prime Minister Zoran Djindjic, but also an attempt to intimidate witnesses and others involved in the trial.
The nonparliamentary Liberal Democratic Party of Cedomir Jovanovic, a former Serbian deputy prime minister and Djindjic's closest associate, also requested that Jocic be relieved of duty.
The party said in a statement that Vukojevic was killed because he was the only remaining witness who directly pointed to a connection between incumbent Serbian Prime Minister Vojislav Kostunica's closest associates and the Djindjic assassination, and so that the political background of the assassination could not be revealed.
Jocic told Serbian Radio and Television the Vukojevic murder represented a "showdown among members of the same crime gang" and that it was a consequence of "fear of certain testimonies".
Vukojevic's half-burned body was found on Saturday afternoon on the outskirts of Belgrade by the highway to Zagreb. He was a former policeman and bodyguard of one-time Zemun clan chief Dusan Spasojevic, who was killed in the March 2003 police operation Sabre, and was a witness who turned state's evidence in the Djindjic assassination trial and a trial against members of the Zemun clan, who were accused of numerous murders, kidnappings, extortions and other crimes.
The first indicted in both cases is Milorad Ulemek a.k.a. Legija, a former commander of the Special Operations Units a.k.a. the Red Berets.