Appeals judges at the Yugoslav war crimes tribunal say Serbian far-right leader Vojislav Seselj has breached conditions of his provisional release and must return to the court's cellblock in The Hague.

Seselj, who is accused of recruiting notorious paramilitary forces during the Balkan wars, was released in November for medical treatment in Serbia on condition that he did not interfere with victims or witnesses and that he would return to the tribunal if summoned.

But Seselj told a news conference after arriving back in Belgrade that he would not return voluntarily. Prosecutors say that statement breached conditions of his release and appeals judges agreed in a written decision released Monday.

Seselj surrendered to the court in 2003 and is awaiting verdicts in his trial.