Ukrainian President Viktor Yanukovich says he has ordered a probe into the alleged beating of the country's jailed former prime minister and opposition leader, Yulia Tymoshenko.

Mr. Yanukovich made the statement about his political rival Thursday, one day after Ukraine's commissioner for human rights said a personal examination confirmed that Ms. Tymoshenko has bruises on her body.

A lawyer for Ms. Tymoshenko, who is jailed on what the European Union and United States say are politically motivated charges, said prison guards beat her up Friday while moving her to a hospital for treatment. The lawyer, Serhiy Vlasenko, said her arms and stomach were bruised from the incident.

He also said Ms. Tymoshenko has been on a hunger strike since the alleged beating.

Since that statement, German President Joachim Gauck has cancelled his planned attendance at meeting in the Ukrainian Black Sea resort of Yalta next month to protest Ms. Tymoshenko's situation. And EU foreign policy chief Catherine Ashton has announced she is “deeply preoccupied” with the issue.

Prosecutors have admitted Ms. Tymoshenko was taken to a hospital against her will, but deny allegations she was beaten. She had refused to go to the hospital voluntarily because she does not trust the government's doctors.

The former prime minister has complained of severe back pain and has asked for medical treatment monitored by foreign doctors.

Last year she was sentenced to seven years in jail on charges of abuse of office in a 2009 gas deal with Russia. She is now standing trial on tax evasion charges that could extend her jail time to 12 years.

Ms. Tymoshenko denies the charges and argues they are part of a campaign by President Yanukovych to remove his strongest political rival.