A defiant Slobodan Milosevic has denounced his arrest as "politically staged" in an appeal demanding his release in a statement written from his cell.
The statement contained a startling admission that he financed the Serb rebellions that bloodied Bosnia and Croatia in the early 1990s.
The former president is jailed in Belgrade's Central Prison as authorities build a case of alleged corruption and abuse of power against him.
Answering accusations that he illegally channelled millions of dollars to secret funds, Mr Milosevic acknowledged for the first time that he funnelled cash to ethnic Serb forces in neighbouring Bosnia and Croatia, which unsuccessfully fought to prevent those republics from breaking away from Yugoslavia.
Mr Milosevic's appeal said he financed the purchase "of weapons, ammunition and other needs" for the Bosnian Serb and Croatian Serb armies.
"These expenses could not, as a state secret, be accounted for in the state budget," he said, denying police allegations that he used the cash for personal gain.
But in attempting to account for £250m in Yugoslav dinars and German marks that authorities say he took from the country's treasury, Mr Milosevic risked building the case against himself at another court - the UN war crimes tribunal in The Hague, Netherlands.
The tribunal already has indicted him for crimes against humanity in his brutal crackdown on ethnic Albanians in Kosovo in 1999. Prosecutors say they are also working to charge him with triggering atrocities during the wars in Croatia and Bosnia.
The Belgrade government has won critical support from the United States when the State Department announced that Milosevic's arrest showed sufficient good faith for it to release $50m in aid.
But US Secretary of State Colin Powell cautioned that unless Yugoslavia continues to co-operate with the UN court, the United States will withhold support for an international donors' conference to help the shattered Yugoslav economy.