The lawyer for war crimes suspect Ratko Mladic says he has formally filed an appeal against the former general's detention.
The move will likely delay his extradition for at least a day.
Attorney Milos Saljic asked for a battery of doctors to examine the 69-year old.
Mladic was arrested last week after 16 years on the run, and is said to have suffered at least two strokes.
Mr Saljic says he has mailed his appeal from an unspecified post office in Belgrade on Monday.
Court officials will now need to wait for it and review it before moving forward with the case.
Bruno Vekaric, Serbia's deputy war crimes prosecutor, says Mladic is employing delaying tactics and that nothing should prevent his extradition to the international war crimes court in The Hague, Netherlands.
On Sunday evening Protesters throwing stones and bottles clashed with baton-wielding riot police in Belgrade after several thousand Serbian nationalist supporters of Mladic rallied outside the parliament building to demand his release.
About 100 people were arrested and 16 minor injuries were reported.
That amounted to a victory for the pro-Western government, which arrested Mladic on Thursday, risking the wrath of the nationalist old guard in a country with a history of much larger and more virulent protests.
