Tymoshenko, 51, began a hunger strike last Friday to protest alleged mistreatment. She says prison guards punched her in the stomach while she was being taken to hospital, against her will, for treatment of chronic back pain resulting from a slipped disc.
News of the ex-prime minister's continuing ill health comes after four blasts injured 27 people Friday in Ukraine's eastern city of Dnipropetrovsk, which is also Tymoshenko's hometown. Officials have quickly launched an investigation, yet no developments have been reported.
Tymoshenko's party claims the attacks could be a government attempt to detract attention from their leader's condition.
Mykola Tymenko, deputy parliament speaker and member of Tymoshenko's party, indicated he does not rule out the possibility that President Viktor Yanukovych's deputies organized the explosions, the Associated Press reported.
German doctors sent to examine Tymoshenko's condition have expressed concern about the quality of her treatment, and have warned that her hunger strike could soon prove life-threatening given her weakened state.
She is no longer the courageous and assertive woman we met in February, Dr. Karl Max Einhaeupl of Berlin's renowned Charite hospital told Reuters.
Her slipped disc is causing her great pain because she wasn't adequately treated at the start of her illness, causing the problem to become chronic.
The hunger strike is for sure not life-threatening in the first two, three days. However, given her reduced psychological and physical condition it could reach a life-threatening stage at some point, he added.
There are doubts that the jailed opposition leader is able to receive the treatment she needs in Ukraine due to the lack of equipment and experienced medical staff there, the experts noted.
I appeal to the Ukrainian president to be guided by humanitarian values and let her travel abroad to [western] Europe to receive treatment, Einhaeupl said.
Tymoshenko's daughter and husband have also expressed concern.
She is very weak, she hasn't eaten for seven days, only drinking water. Prison officials threaten that they will force feed her, Eugenia Tymoshenko told the AP.
Oleksandr Tymoshenko, who was granted asylum in the Czech Republic, said the government wants his wife dead.
Everything that has been happening to Yulia Tymoshenko is a rehearsal of her physical destruction - a murder that the authorities have been planning to carry out since the beginning of repression against her, he said to the AP.
Photos said to be taken Wednesday by Ukraine's top human rights official Nina Karpachova show a frail-looking Tymoshenko with bruises on her arms and abdomen, the alleged results of assault by prison staff.
President Yanukovych launched an investigation into the allegations on Thursday after pressure from abroad. The events even prompted German president Joachim Gauck to cancel his summer trip to Ukraine over concerns about Tymoshenko's treatment.
Relations between Ukraine and the European Union have been strained since Tymoshenko was convicted last year of abusing her power as prime minister while securing a gas deal with Russia in 2009. She also faces separate embezzlement charges relating to when she served as head of state-owned United Energy Systems in the 1990s.
Tymoshenko gained popularity when she helped lead the country's 2004 Orange Revolution in protest of a corrupt election that pro-Russia Yanukovych falsely won. The election was overturned by the Supreme Court and Tymoshenko formed a government along pro-Western lines.
Yanukovych subsequently defeated Tymoshenko in presidential elections held in 2010.