Ukraine's former prime minister Yulia Tymoshenko, whose jailing last year has soured the former Soviet republic's relations with the West, has been moved to hospital where she is expected to receive treatment for back pain.
The imprisonment of Tymoshenko, a fierce opponent of President Viktor Yanukovich, has become a key issue in Ukraine's relations with the European Union, which saw her prosecution as an example of selective justice.
The European Court for Human Rights, which is looking into her appeal against last year's conviction on abuse-of-office charges, has urged Ukraine to ensure Tymoshenko receives proper medical treatment.
Tymoshenko, 51, who is now on trial on graft charges, has suffered from back pain for months, her lawyers and family say, and has refused to attend the fresh hearings.
"Tymoshenko has already arrived at the clinic where she will be offered a range of procedures recommended by German and Ukrainian doctors," the state prison service said in a statement late on Friday.
Tymoshenko had previously refused to move to the hospital, which belongs to the state-owned railway company and is near to the prison were she is held in the city of Kharkiv.
Tymoshenko was convicted in October of abusing her power as prime minister in brokering a 2009 gas deal with Russia which Yanukovich's government says ran against national interests and made energy imports exorbitantly expensive.
In the fresh trial, she faces charges of tax evasion and attempted embezzlement which carry a sentence of up to 12 years.
Tymoshenko has denied any wrongdoing in both cases, dismissing them as part of a campaign of repression against the opposition by Yanukovich's government.
The European Union has warned Ukraine that its members would not ratify key bilateral agreements on political association and free trade while Tymoshenko remains in prison.
Tymoshenko was one of the leaders of the 2004 Orange Revolution which doomed Yanukovich's first bid for the presidency and went on to serve twice as prime minister. She lost the 2010 presidential vote to Yanukovich in a close race.