The lawyer for former Ukrainian Prime Minister Yulia Tymoshenko says his client wants to be seen by her own doctor for an undisclosed illness that he said struck quite suddenly.

Ms. Tymoshenko and her lawyer were back in a Kyiv court Thursday for her weeks-long trial on abuse of power. It is not clear what ailment she suffers from, but the lawyer said she was not fit to stand trial at present.

The judge noted that Ms. Tymoshenko had refused to undergo testing at the jail's medical facilities Thursday.

Ms. Tymoshenko responded by saying, “I demand to be seen by a doctor I trust.”

The prominent opposition leader was jailed on charges of signing a bad gas deal with Moscow when she was prime minister in 2009. She denies the charges and has said they are aimed at keeping her out of politics.

The United States and Europe have spoken out against Ms. Tymoshenko's detention and called for her immediate release.

Ms. Tymoshenko, a key opponent of President Viktor Yanukovich, was a close ally of former President Viktor Yushchenko. Mr. Yushchenko, who eventually beat bitter rival Yanukovich after a disputed election that led to Ukraine's Orange Revolution street protests, was poisoned during his presidential campaign run and nearly died.