Serbian prosecutors have filed charges against a far-right leader for burning a Croatian flag while defying orders to return to the U.N. war crimes tribunal.

Appeals judges at the tribunal in The Netherlands ruled Monday that Vojislav Seselj has breached conditions of his provisional release in November. He has said he wouldn't return voluntarily.

In a show of defiance, Seselj on Wednesday set a Croatian flag on fire at a Belgrade court where he appeared as a witness in the trial of an associate who has been charged with torching an American flag three years ago.

Seselj, who is accused of recruiting paramilitary forces during the 1990s wars in Croatia and Bosnia, was released for medical treatment on condition that he would return to the tribunal if summoned.