The former general is rumoured to be hiding in Serbia, with the help of ex-military supporters.

Derek Chappell, a Nato spokesman, said no one was arrested in Tuesday's raid, but some items were seized by the troops.

Radovan Karadzic, the wartime Bosnian Serb leader and Mladic's chief, was captured last July in Belgrade and is on trial at the UN's war crimes tribunal in The Hague.

Mladic and Karadzic stand accused of committing war crimes in connection with the 1995 Srebrenica massacre of around 8,000 Bosnian Muslims and the siege of Sarajevo that claimed more than 10,000 lives.