WASHINGTON (Reuters) - The United States called for the release of former Ukrainian prime minister Yulia Tymoshenko on Tuesday, joining European leaders in condemning the conditions of her imprisonment amid allegations that she was beaten.

U.S. Secretary of State Hillary Clinton, in a statement, said recent photos "further call into question the conditions of her confinement" and urged Ukrainian authorities to allow medical treatment and access to the U.S. ambassador.

Tymoshenko, serving a seven-year jail sentence on charges of abuse of office, has been on a hunger strike since last week after she said prison guards forced her to go to a hospital because of her long-term back problems and then beat her.

On Monday, her family said she was bruised and could not move much. They called on Ukrainian authorities to take action, citing her weak condition.

Clinton, the top U.S. diplomat, said the United States was deeply concerned about Tymoshenko's treatment and cited photos from Ukraine's senior human rights official.

"We continue to call for her release, the release of other members of her former government and the restoration of their full civil and political rights," she said in the statement.

Tymoshenko's daughter Yevgenia Tymoshenko, who said she visited her mother in recent days, said on Monday that medical treatment abroad is the only possible solution.

The incident has soured Ukraine's ties with the European leaders, who have condemned it as example of selective justice in the country now ruled by her political arch-rival Viktor Yanukovich.

Yanukovich has ordered an investigation of the alleged beating.

Several European leaders have called off visits to Ukraine and threatened to boycott a major soccer tournament to be played there in June.

Tymoshenko was found guilty last year of abusing her power in brokering a 2009 gas deal with Russia and she still faces tax evasion charges. She has called the charges part of a campaign by Yanukovich to destroy political opposition.

(Reporting by Susan Heavey; Editing by Bill Trott)