European Union and Russia condemn seven-year sentence for former prime minister accused of abuse of office over gas deal

Ukraine shut the book on its flirtation with democracy and European integration on Tuesday when it sentenced former prime minister Yulia Tymoshenko to seven years in prison in a trial widely seen as a political witch-hunt.

The EU said it was "deeply disappointed" in the conviction and vowed to review links with the country. It had issued repeated warnings to President Viktor Yanukovych that a guilty verdict would derail negotiations that had been on the verge of forging unprecedented ties between Brussels and Kiev.

Tymoshenko, flanked by her daughter and husband, appeared defiant as Judge Rodion Kireyev read the nearly four-hour-long verdict on charges that she exceeded her authority when she signed a gas deal with Russia in 2009.

In addition to the seven-year term – the maximum requested by state prosecutors – the judge ordered her to repay 1.5bn hryvna (£120m) in damages incurred by state gas firm Naftogaz, and seized her property. The 50-year-old was also banned from participating in political life for three years after the sentence runs out.

Tymoshenko, visibly angry, responded by telling the court: "Today it has become clear to everyone that the country is ruled by a dictatorship.

"I beg you to unite to overturn this authoritarian regime."

She compared her trial to Stalin's purges, when the Soviet dictator sought to eliminate his perceived enemies, telling the court: "You know very well that the sentence is not being pronounced by Judge Kireyev, but by President Yanukovych."

Tymoshenko has been Yanukovych's chief political rival for nearly a decade, co-leading the Orange Revolution that kept him from coming to power in 2004 as Ukraine bucked Russian influence in favour of forging closer ties with the west.

But as the Orange coalition devolved into bitter political infighting, Yanukovych was elected to office last year, with Tymoshenko becoming chief opposition leader.

William Hague, the British foreign secretary, said her conviction was "deeply concerning" and called into question Ukraine's relationship with the EU.

He said the trial could pose a "major obstacle" to the signature and ratification of a so-called "deep and comprehensive" free-trade agreement, which both Brussels and Kiev had hoped to sign by the end of the year.

Hague said: "Ukraine says it wants to join the EU one day. The UK supports that objective. But that cannot happen until Ukraine can show that it adheres to the highest democratic standards, including respect for human rights, the rule of law and an independent, transparent and fair judicial process."

Lady Ashton, the EU foreign policy chief, said in a statement: "The verdict comes after a trial which did not respect the international standards as regards fair, transparent and independent legal process."

Ukraine's politics, and its relationship with business, remains murky 20 years after the fall of the USSR, while its institutions are woefully unreformed and subject to intense political influence. Tymoshenko herself grew hugely rich in the 1990s and was nicknamed "the gas princess" after her main source of wealth.

The current trial – over a deal that put an end to a ruinous gas war with Russia that left much of eastern Europe freezing in January 2009 – was the culmination of a targeted campaign against the opposition leader that saw nearly a dozen of her associates also arrested.

"In a way this case reminds me of [jailed Russian oligarch Mikhail] Khodorkovsky," said Sergei Markov, a member of Russia's State Duma. "In both cases there are political reasons for the trial."

Ukraine risks becoming an international pariah after Moscow also reacted harshly to the conviction, with the foreign ministry noting that "many states and the world public perceive this entire judicial process as initiated for purely political reasons".

The case, the ministry said, contained "an obvious anti-Russian subtext". Russia has resisted Yanukovych's attempts to renegotiate the gas deal in favour of Ukraine.

Some Ukrainian analysts have speculated that the leadership in Kiev could attempt to save face by overturning the sentence. That would free Tymoshenko from prison but bar her from participating in political life, including next year's parliamentary elections and a 2015 presidential vote. EU officials have said that would not be enough.

Last week, the Ukrainian parliament threw out proposed amendments to the criminal code that would have decriminalised the articles under which Tymoshenko was convicted. Yanukovych hinted late on Tuesday that plan was still a possibility.

"[The verdict] has made the European Union anxious and we understand why this is so," Yanukovych said, news agencies reported from Kiev.

"Today the court took its decision in the framework of the current criminal code. This is not the final decision.

"Beyond doubt this is a regrettable case which is impeding the European integration of Ukraine today."

Amnesty International issued a statement calling for Tymoshenko's immediate release.