Mrs Plavsic, who was was invited for talks in London by the Foreign Office on the strength of her new-found reputation as a moderate, cut short her British visit amid reports of opposition to her planned drive against corruption.
At Belgrade airport on Sunday night, in spite of being titular head of an entirely independent state, she was grabbed by the police of President Slobodan Milosevic of Serbia and held for an hour- and-a-half. She was then transported to Bijeljina, in north-east Bosnia, where she was detained overnight by her own police in the village of Dvorovi.
Yesterday the "President" was set free and returned to the Bosnian Serb city of Banja Luka with an escort provided by S-For, the international peace-keeping force in Bosnia. They were reported to have secured the presidency building in Banja Luka against possible attack.
Mrs Plavsic was one of a trio of Serb ultra-nationalists led by Radovan Karadzic who plunged Bosnia into a bloodbath from 1992-5 by trying to carve an ethnically pure Serb state out of the mixed Muslim-Christian former Yugoslav republic.
Unlike Mr Karadzic she was not indicted for suspected war crimes by the UN tribunal in the Hague, but until recently was seen as the most hardline of the lot. President Milosevic's journalist wife Mirjana famously accused her of being a Nazi.
Her troubles proceed not from being "soft" on Muslims, but from her opposition to corruption which, as a rabid but sincere nationalist, she devoutly opposes. Mr Karadzic and his close ally, Momcilo Krajisnik, have had no scruples about draining the last drops out of the bankrupt Bosnian Serb state to line their pockets. Mr Karadzic has made his cash through his monopoly on smuggled cigarrettes. Mr Krajisnik and his brother have lined their pockets by sharing out monopolies on spirits and petrol. They are reported in the Belgrade media to have stashed their fortunes away in private banks in Russia.
Mrs Plavsic, who assumed the Bosnian Serb leadership from Mr Karadzic after he was indicted by the UN war crimes tribunal decided to crack down on the private mafias after a meeting with Madeleine Albright during the US Secretary of State's recent tour of former Yugoslavia. She also told Ms Albright she had swung behind the "moderate" camp on the question of a single currency for Bosnia - a big irritant to the mafia men, who have no desire to see the Bosnian Serbs' worthless currency replaced by something more stable.
Just prior to her return from London, she announced the sacking of the Bosnian Serb police chief, Dragan Kijac.
Her detention in a police cell in Bijeljina will raise a bitter smile from Bijeljina's surviving Muslims. Mrs Plavsic first achieved real fame by publicly kissing the Serb paramilitary leader Zeljko Raznjatovic, "Arkan" after his forces had stormed the town in April 1992 and murdered many local leaders of the Muslim community.
t The Hague (AP) - UN war crimes prosecutors will give secret indictments to "authorities ready, willing and able to execute them," Chief Prosecutor Louise Arbour said.
Ms Arbour was reacting to Friday's arrest by the UN of Slavko Dokmanovic, a Serb suspect in the massacre of 260 Croats in the eastern Croatian town of Vukovar in 1991. His arrest marked the first time UN authorities have held an indicted suspect in the former Yugoslavia.