Russian gas company Gazprom in 2009 cut gas supplies briefly to Ukraine over contract issues and debt. Ukrainian Prime Minister Yulia Tymoshenko secured a revised deal that imposed strict requirements on Kiev. Prosecutors say the deal cost the country around $440 million at a time when Ukraine's economy was greatly affected by the global economic meltdown.
Tymoshenko, now an opposition leader, was charged with "exceeding authority" in a case involving a 2009 natural gas deal with Russian company Gazprom. She claims the case is politically motivated.
The prosecutor general's office in Kiev said it opened a separate case involving the gas deal and called in Tymoshenko's deputies Oleksandr Turchynov and Hryhoriy Nemyrya for questioning, Russia's state-run news agency RIA Novosti reports.
"There is no legal position or economic substantiation in these cases," Turchynov was quoted as saying.
Moscow and its European customers since 2009 have pressed for alternative delivery routes around Ukraine, though Kiev maintains the country is still a viable transit nation.