|Police said their attention is on extremist groups they fear may cause trouble [EPA]
Serb authorities have tightened security ahead of protests by supporters of Ratko Mladic, the former Bosnian Serb general awaiting extradition to the Hague to face war crimes charges.
Extreme right-wing groups urged their supporters, mostly soccer hooligans, to join Sunday's planned rally in front of parliament in downtown Belgrade, the capital.
The rally, organised by the ultranationalist Serbian Radical Party, is seen as a test about whether Mladic still enjoys popular support after 16 years as a fugitive.
A Serbian judge ruled on Friday the 69-year-old had a medical commission "which has determined he is fit for further proceedings".
Police officials said they had turned attention to groups planning the protests.
"Additional attention has been focused on the extremist groups these days," said Ivica Dacic, Serbia's police chief. "We are taking measures to prevent the escalation of extremist behavior."
Mladic's lawyer, Milos Saljic, said the former Bosnian Serb military commander knew he would be extradited to a UN war crimes tribunal but wanted time to rest before the trip.
Saljic told reporters that Mladic did not know exactly when he would be extradited to the tribunal in The Hague, Netherlands, "but he would like to recover a little bit first".
Mladic, who is being held in a Serbian jail, could be extradited as early as Monday, if a judge rejects his appeal of a decision to move him to The Hague.
His defence team and family have said he suffers from several health problems.
Bruno Vekaric, the prosecutor, said the court also was considering Mladic's request to visit the grave of his daughter, Ana, who committed suicide in 1994 at age 23. Vekaric said he would not object, but there could be security risks.
Mladic also was granted a visit on Saturday afternoon by Serbia's parliament speaker, Slavica Djukic Dejanovic, a psychiatrist.
She said her visit was strictly as a "doctor," and she declined to discuss it.
Mladic's son Darko told reporters in front of the Belgrade court that the former fugitive looked a bit better than he did on Friday, but seemed unaware of the situation he faces.
"If you were able to talk to him for five minutes, you would know what I'm talking about," Darko Mladic said, reiterating a family appeal that Mladic be placed in a hospital.
He also repeated Mladic's call against violence by his supporters, saying the protests should be peaceful.