Carla del Ponte, chief prosecutor for war crimes in the former Yugoslavia, has said she believes Gen Ante Gotovina is hiding in a monastery in Croatia.
Ms del Ponte’s spokeswoman told the BBC News website that the Vatican had refused to help in the search for him, despite being in a position to do so.
Gen Gotovina has been charged with the deaths of 150 Serb civilians in 1995.
Forces under Gen Gotovina’s command are accused of killing scores of Serbs and expelling up to 200,000 from the Krajina region, now part of Croatia.
Many in Croatia regard him as a national hero.