A column of police jeeps possibly carrying the war crime suspect Goran Hadzic left the special court building in Belgrade on Friday morning, DPA reported.
It was, however, not immediately clear whether Hadzic was being transferred to the International Criminal Tribunal for the former Yugoslavia (ICTY) in The Hague.
The television station B92 quoted sources as saying that Hadzic was being taken to Novi Sad, 80 kilometres west of Belgrade, to see his mother, who is reportedly on her deathbed.
He may be taken to the airport directly from Novi Sad, B92 said.
Hadzic, 52, was arrested Wednesday on charges of war crimes after seven years on the run.
As a rebel Serb leader in Croatia in the 1990s, he has been accused of crimes against humanity and violations of laws and customs of war, including the massacre of nearly 300 Croat prisoners at Vukovar in 1991.
Hadzic waived his right to appeal the extradition and may be put on a plane for transfer to The Hague at any moment.