Former Ukrainian Prime Minister Yulia Tymoshenko alleged on Tuesday that guards at the prison where she is being held severely beat her and said she has begun a hunger strike.

Prosecutors denied the charge, saying that prison guards had taken Tymoshenko to a nearby hospital for treatment of an existing medical problem against her will, but that she was not beaten.

Tymoshenko, the country's top opposition leader, is serving a seven-year prison term on charges of abusing her powers during negotiations about gas supplies with Russia. The West has strongly condemned the verdict as politically motivated and threatened to freeze cooperation with Ukraine.

Tymoshenko, 51, denies the charges, saying they are part of a campaign by her longtime foe, President Viktor Yanukovych, to bar her from politics. Yanukovych, who narrowly defeated her in the 2010 presidential race, has denied involvement in the Tymoshenko case and said the investigations against her are part of an anti-corruption effort.

The opposition leader is suffering from a severe spinal condition, and a group of German doctors who examined her recommended that she be treated at a specialized medical clinic. Instead, she was taken on Friday night to a local clinic in the eastern city of Kharkiv where her prison is located. She refused treatment and was moved back to prison on Saturday.

On Tuesday, Tymoshenko said in a statement that she resisted being taken to the local hospital because she didn't trust government-appointed doctors but that prison officials transported her there by force.

She alleged that three big guards entered her jail cell, covered her with a bedsheet, punched her in the stomach when she started resisting, twisted her arms and legs, and carried her outside in the bedsheet, causing her to lose consciousness because of the back pain such handling caused.

"I thought that the last minutes of my life have come," Tymoshenko said in the statement on her website. "At some point I simply passed out from the horrible pain and came to already in a hospital ward." Tymoshenko's lawyer, Serhiy Vlasenko, said she still had a large bruise on her stomach nearly four days after the alleged beating.

Regarding the hunger strike, Tymoshenko said she has refused food since Friday night in order to attract "the attention of the democratic world to what is happening in the center of Europe, in a country called Ukraine."

Prosecutors confirmed that Tymoshenko had been taken to the hospital against her will, but claimed that prison officials had acted within the law and insisted there was no evidence to support the allegations of beating.

"The person got packed, dressed and then lied down on the bed and said 'I will not go anywhere'," Kharkiv regional prosecutor Henadiy Tyurin told reporters in remarks confirmed by his office. "According to the law ... the prison service has the right to use physical measures. She was picked up, carried to the car and taken to the hospital."

Prison officials denied the use of force against Tymoshenko and threatened to sue anyone defaming them.

Dr. Iryna Fursa, a neurologist who examined Tymoshenko at the Kharkiv clinic, charged that the former prime minister was conscious when she arrived, the Interfax news agency reported.

In Germany on Tuesday, the country's foreign minister, Guido Westerwelle, voiced "deep concern" about Tymoshenko's condition and her announced hunger strike. He urged Ukrainian authorities to finally give her appropriate medical treatment.