Nato troops have released the son of Bosnian Serb wartime leader Radovan Karadzic, who is wanted for war crimes.
Nato has raided several premises hunting the main fugitives
Aleksandar "Sasa" Karadzic was handed over to Bosnian Serb police in Pale where he was arrested 10 days ago.
"This is a part of our ongoing strategy to detain war crimes indictees and disrupt their support network," said Nato spokesman Derek Chappell.
Radovan Karadzic and his military commander Ratko Mladic top the UN war crimes tribunal's most-wanted list.
The two men are accused of genocide over the killing of about 8,000 Muslim men during the Srebrenica massacre in July 1995.
Aleksandar Karadzic was detained on suspicion of giving support to his father.
The Nato spokesman did not give any details on young Karadzic's detention and questioning.
Mr Chappell only said the "investigation is ongoing".
Nato has unsuccessfully raided several sites where Mr Karadzic was suspected of hiding.
International security agencies - speaking on condition of anonymity - told BBC Radio Four's File on Four programme this month 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.