Nato troops have arrested the son of Bosnian Serb wartime leader Radovan Karadzic, who is wanted for war crimes.
International troops have been hunting Mr Karadzic for years
Aleksandar "Sasa" Karadzic was detained in Pale, the Bosnian leadership's stronghold during the 1992-1995 war.
Witnesses said he was led away in handcuffs and a flak jacket; a hood was put over his head as he was driven away and then flown out by helicopter.
A statement from Nato said the arrest happened without incident and the operation was ongoing.
It said Aleksandar Karadzic was suspected of giving support to a war crimes suspect indicted by the International Criminal Tribunal for the Former Yugoslavia.
The statement said he "may have information vital to the goal of locating indicted war criminals or identifying their supporters".
"Fugitive war crime suspects and their supporters represent a major threat to sustained peace in Bosnia and Hercegovina and ultimately to the country's progress and development," it added.
The arrest comes four days before the anniversary of the massacre of nearly 8,000 Muslim men and boys at Srebrenica in eastern Bosnia. Radovan Karadzic has been accused of political responsibility for the massacre.
His wartime military commander Ratko Mladic, also on the run, is charged with genocide for the 1995 Srebrenica massacre.
Last week, international security agencies speaking on condition of anonymity told BBC Radio Four's File on Four programme that Radovan Karadzic was believed to be in a remote part of north-west Montenegro.
Peacekeeping troops in neighbouring Bosnia cannot take action as their jurisdiction does not cover Montenegro, which is part of Serbia and Montenegro.