The 2009 agreement between the state energy firm Naftogaz and Russia's gas giant Gazprom ended a pricing dispute between Ukraine and Russia which had led to disruptions of gas supplies to some EU countries. It was greeted with relief by Europe at the time.

But the government under Yanukovich, who beat Tymoshenko in a fight for the presidency in February 2010 and forced her out as prime minister, says the deal saddled Ukraine with an exorbitant price for Russian gas.

Taking the line argued by the prosecution, the judge said Tymoshenko had exceeded her authority "for criminal ends" by railroading Naftogaz into signing the agreement.

In addition to the jail sentence, he imposed a fine of 1.5 billion hryvnias (US$188 million) which he said was the estimated loss caused to Naftogaz by her actions.

Justifying the seven-year sentence, he said he had not found any "extenuating circumstances" to reduce the prison term nor any signs of remorse from Tymoshenko.

Her lawyers said they would appeal.

Tymoshenko, who denied any wrongdoing, has said the trial was a "lynching" by Yanukovich and by those whom she describes as the "criminal oligarchy" backing him.