KIEV, Dec. 23 — A Ukrainian court on Friday kept former Premier Yulia Tymoshenko in jail on charges of abuse of office, defying renewed Western pressure to release the country’s top opposition leader.

The Kiev Appeals Court upheld a lower court’s guilty verdict and seven-year sentence for Tymoshenko, 50, in a decision her top aide called President Viktor Yanukovych’s “personal vengeance.”

Tymoshenko was convicted in October of overstepping her authority while negotiating a natural gas contract with Russia in 2009.

The U.S. and the European Union have sharply criticized Tymoshenko’s imprisonment as politically motivated and demanded her release. The EU this week refused to sign a key partnership deal with Kiev over the Tymoshenko case.

Yanukovych, Tymoshenko’s longtime foe, said the courts and law enforcement agencies were independent and he would not intervene.

Tymoshenko’s top ally, Oleksandr Turchynov, accused Yanukovych of trying to get rid of his main political rival.

“This verdict is Yanukovych’s personal vengeance against Yulia Volodymyrovna Tymoshenko as his main opponent — stronger, more powerful,” Turchynov said, The Associated Press reported. “After this decision, the president becomes a dictator of a criminal regime.”

Tymoshenko has spent more than four months in a Kiev jail after being charged with contempt of court during her trial. She claims to have developed severe back and skin problems while in custody and accuses the authorities of denying her proper medical care.

Prosecutors spokesman Yuriy Boychenko said it was unclear whether Tymoshenko would now be sent to a provincial prison to serve her term or would remain in Kiev while a separate case that has been opened against her is investigated.

Germany’s top human rights official said the Kiev court missed an opportunity to uphold the rule of law.

“The verdict against Yulia Tymoshenko is another setback to Ukraine’s path of rapprochement with the European Union, which is also a union of values,” Markus Loening said in a statement. “Among those values is that political differences must be dealt with through political competition.”

Tymoshenko said Thursday she would boycott all legal proceedings in Ukraine and has lodged an appeal with the European Court of Human Rights, claiming it is pointless to seek justice in Ukraine as long as Yanukovych is in power. However, that process could take months and it is unclear if a decision by the Strasbourg-based court would be legally binding in Ukraine.

Tymoshenko’s office says that if the Strasbourg court were to rule that Tymoshenko’s right to a fair trial was violated, she would have to be released from jail.

But some independent legal experts have said that while Ukraine’s Supreme Court would be required to review the case, it wouldn’t necessarily be obliged to overrule the decision of the lower courts. (ap/ez)