Ratko Mladic is already on a plane to The Hague and the process to extradite him to the UN war crimes tribunal has started, Serbian Justice Minister Snezana Malovic told a special news conference on Tuesday.

The minister said Mladic was escorted to the Belgrade airport earlier on Tuesday under heavy security.

Witnesses said two convoys of jeeps and police cars headed directly to the airport after leaving the premises of the Special Court, Xinhua reported.

Mladic's lawyer, Milos Saljic, said a three-member chamber of the Special Court rejected an appeal against the extradition for medical reasons.

Saljic said earlier that the Mladic family is in shock and had no forewarning of the arrest. The family asked for the official declaration of Mladic's death a year ago, saying they had had no contact with him in seven years and assumed he was dead due to failing health.

Mladic's arrest and extradition sparked a violent clash between protesters and police on Sunday in Belgrade. The Radio Television Republika Srpska (RTRS) reported that as many as 10,000 people held a rally on Tuesday in support of Mladic in the central square of the Bosnian Serb capital, Banja Luka.

Mladic is a fugitive long wanted by the International Criminal Tribunal for the former Yugoslavia (ICTY) for alleged genocide and crimes against humanity, most notably for the summary execution of captured Bosnian Muslim soldiers after the fall of the UN protected zone of Srebrenica in 1995.

He was the most high-profile fugitive still at large, dating back to the civil conflicts that erupted during the breakup of the former Yugoslavia in the 1990s. He had been in hiding since 1996, according to Xinhua.