Former Ukrainian Prime Minister Yulia Tymoshenko's guilty verdict and seven-year jail sentence was upheld Friday by a Ukrainian appeals court.

The court has left the (original) ruling unchanged, a spokeswoman for the appeals court said, Reuters reported.

Tymoshenko, 50, was convicted in October of abusing her powers while negotiating a natural gas import contract in Russia in 2009. The United States and the European Union have condemned the ruling, alleging that the conviction is a ploy to keep the top opposition leader behind bars in order to keep her from elections.

But Ukrainian President Viktor Yanukovych, who Tymoshenko fiercely opposes, adamantly refuses to release her.

On Thursday, Teymoshenko and her lawyers said they would boycott her appeals hearing, saying she would not take a part in this shameful process.

Instead, she and her attorneys plan to pursue her case in the European Court of Human Rights, which has promised to give it priority due to the serious and sensitive nature of the allegations raised, the court said, according to news reports.

In a statement published by her political party Btkivschyna, Tymoshenko said she would continue her activities from behind bars, Reuters reported.

...No matter where I am -- in or out of prison -- all my life is dedicated to the idea of changing this evil court of history and restoring every Ukrainian's self-belief and trust to his or her state, Tymoshenko said.

On Nov. 15, the Ukrainian parliament rejected a move to downgrade Tymoshenko's abuse-of-power conviction to a misdemeanor charge that would see her release, maintaining that the former prime minister overstepped her powers when she negotiated the Russia gas contract, which, ultimately, was deemed harmful for the Ukrainian economy.

Tymoshenko insists that the legal woes are a political lynching by her foe, Yanukovych, who wants to rid himself of a political rival. Last year, Tymoshenko lost to Yanukovych in a bitter battle for the presidency, garnering 45.47 percent of the votes.