Ukraine’s jailed opposition leader Yulia Tymoshenko halted a 20-day hunger strike after she was moved to a hospital to defuse a crisis overshadowing the Euro 2012 football.

Ukraine’s prison authorities transferred Ms Tymoshenko from her jail in the eastern city of Kharkiv to the hospital where she will receive treatment from a German doctor for severe back pain.

The doctor confirmed that the 51-year-old former Prime Minister had ended the hunger strike she began in April in protest at allegedly being roughly handled by prison guards.

“She has halted her strike and we are now building up towards a normal nutrition regime,” Lutz Harms of Berlin’s prestigious Charite hospital told reporters. “This process will take several days.”

“She is very weak and we will need to wait several days for her situation to stabilise,” said Dr Harms. He said that for the moment Ms Tymoshenko was taking in just water and juices and would only start eating food later.

According to her daughter Yevgenia, Ms Tymoshenko lost 10 kilograms while refusing food.

“We will start a thorough therapy programme which will take some time − most likely it will take at least eight weeks and up to several months,” the doctor said.

US Senator John McCain said he was pleased Ms Tymoshenko ended her hunger strike, but he called on authorities to now free all political prisoners.

“While this is a welcome step, the fact remains that Ms Tymoshenko’s detention is the result of the Ukrainian government’s selective and political prosecution of its peaceful democratic opponents in the country,” Mr McCain said in a statement.

Ukraine is facing a possible extensive EU boycott of the Euro 2012 matches it is co-hosting with Poland in June over its treatment of Ms Tymoshenko, who was jailed for seven years in October after a trial condemned by the West.

The authorities are hoping the hospital transfer will slacken the Western pressure on Kiev as the move complies with a key demand of Ms Tymoshenko to be treated by a foreign rather than a Ukrainian specialist.

The prisons service said the former Prime Minister left the jail in Kharkiv at 7 a.m. (0400 GMT) and arrived at the hospital, a state establishment run by Ukrainian railways, one hour later.

Kharkiv is one of four Ukrainian cities that will stage Euro 2012 matches in what has to be the biggest showcase for Ukraine since it won independence in the collapse of the Soviet Union.

The prisons service said that during her transfer Ms Tymoshenko made no complaint about her health.

Dr Harms, a neurologist who will be assisted by a Ukrainian team, was earlier confirmed by the authorities as Ms Tymoshenko’s official doctor during her hospital stay.

Ms Tymoshenko faces a new trial on May 21 in a separate case where she is accused of tax evasion but the doctor said it was “highly improbable” that she would be fit enough to attend. Ms Tymoshenko is confirmed to be suffering from a slipped disc in her spine but supporters say even before her hunger strike she was extremely frail and unable to walk.

The opposition leader had previously demanded to be treated outside Ukraine, fearing that she could be deliberately infected or poisoned in a Ukrainian establishment.

The European Union has expressed concern that the convictions of Ms Tymoshenko and several of her former ministers were politically motivated and noted that the abuse of power charges would never have come to court in an EU state.

Ms Tymoshenko was found guilty of causing losses of $190 million (€147 million) to the state gas firm in agreeing a 10-year contract for gas imports for Russia in 2009 on terms deemed overly advantageous to Moscow.