( CNN ) -- Former Ukrainian Prime Minister Yulia Tymoshenko , serving a seven-year sentence after last year 's conviction on a charge of abuse of authority , has been on a hunger strike for four days because she was beaten unconscious in prison last week , she said Tuesday . But the prosecutor said Tuesday that his office immediately investigated Tymoshenko 's claim and did n't find proof to substantiate her allegations . A medical expert was sent , but Tymoshenko refused an examination , said Gennady Tyurin , general prosecutor of Kharkiv region . He said he has declined to open a criminal case . `` The investigation is over , '' Tyurin said . Last October , a Ukrainian court found Tymoshenko guilty of abuse of authority for signing gas contracts with Russia and sentenced her to the seven-year prison term . Prior to the alleged beating , Tymoshenko was discussing with officials a transfer Monday to a hospital for health reasons , she said . But on Friday evening , her cell mate left the cell , and then `` three sturdy men '' entered , threw a bed sheet over her , dragged her off the bed and applied `` brutal force , '' she said in a statement . `` In pain and despair , I started to defend myself as I could and got a strong blow in my stomach through the bed sheet , '' she said in a statement . Tymoshenko was dragged `` into the street , '' she said . `` I thought these were the last minutes of my life . In unbearable pain and fear I started to cry and call out for help , but no help came . '' She fell unconscious , and when she came to , she was in a hospital ward , she said . Tymoshenko went on her hunger strike the day after the beating , Saturday , she said . She stopped taking food `` to draw attention of the democratic world to things happening in the center of Europe , in the country named Ukraine , '' she said . Tymoshenko charged that `` the president of Ukraine is steadily and pedantically building a concentration camp of violence and lack of rights . '' She is asking for a `` public international investigation '' into the administration of President Viktor Yanukovych and added , `` we must do everything possible to remove the Yanukovych regime . '' In April 2011 , the Ukraine 's Prosecutor General 's office opened a criminal case charging Tymoshenko with signing overpriced gas deals with Russian energy provider Gazprom that inflicted damages to the country amounting to more than 1.5 billion hryvnas ( almost $ 190 million at the current exchange rate ) and that Tymoshenko had allegedly no right to sign . The court ruled Tymoshenko must repay the money , and she is banned from holding public office for three years . Tymoshenko narrowly lost to Yanukovych in a presidential election in February 2010 , and she became his fiercest opponent . She has repeatedly brushed off all charges against her as political , calling the trial a `` farce '' and naming the judge a `` stooge of Yanukovych 's administration , '' appointed to `` fabricate '' the case . Amnesty International has slammed the verdict as `` politically motivated '' and called for the release of Tymoshenko , who was prime minister from January to September 2005 and December 2007 to March 2010 . CNN 's Michael Martinez contributed to this report .
Ukraine 's former prime minister , Yulia Tymoshenko , has n't taken office since Friday night . She is in prison serving a seven - year sentence for abuse of power . The prosecutor and his office investigated and found no ` ` proof '' of her guilt .