The UN International Criminal Tribunal for the former Yugoslavia has ruled that Serbian ultranationalist Vojislav Seselj had breached conditions of his provisional release and ordered his return to detention at The Hague.
Seselj, 60, is accused of recruiting notorious paramilitary forces during the Balkan wars in the 1990s.
Seselj was released in November so he could be treated for cancer, on condition that did not interfere with victims or witnesses and would return to the court if summoned.
But Seselj said he would not return voluntarily.
Belgrade described the March 30 ruling as "confusing," and said it would decide in the coming days what action to take.
A European Parliament resolution in November slammed what it described as Seselj's "incitement to hatred and encouragement of territorial claims and his attempts to derail Serbia from its European path” since his return to Belgrade.