A spokeswoman for the Nato-led Stabilisation Force said Mr Seselj was told to leave because of his anti-Dayton views.

Mr Seselj was visiting the Bosnian Serb President, Nikola Poplasen, who is head of the Bosnian Serb wing of Mr Seselj's nationalist Radical Party.

He left the town of Banja Luka in the early hours of Saturday morning under a Bosnian Serb police escort and headed for the Yugoslav border.

Stabilisation Force troops earlier blocked access to the town centre, and surrounded Mr Seselj's hotel, demanding that he should leave.

Mr Westendorp banned Mr Seselj from entering the Bosnian Serb republic during the September election campaign, because of his negative statements on the role of the international community in Bosnia.

In a statement made from his hotel before leaving, Mr Seselj said that the Bosnian Serb republic was under American occupation, and that Mr Westendorp's behaviour was in contravention of the Dayton peace agreement.