Excerpts of documents from the Prosecutor General's Office allege imprisoned ex-Prime Minister Yulia Tymoshenko ordered the killing of Yevhen Shcherban in 1996, RIA Novosti reported.
Shcherban, a businessman and member of the Ukrainian parliament, and his wife were shot dead at an airport in eastern Ukraine in 1996.
Prosecutor General Viktor Pshonka last week alleged that Tymoshenko and another former prime minister, Pavlo Lazarenko, ordered the killings.
The excerpted documents say the ex-prime ministers paid $2.82 million for the assassinations.
The documents allege that Shcherban had blocked a plan by United Energy Systems of Ukraine, which Tymoshenko headed, to become the exclusive gas trader in the Donetsk region.
Tymoshenko is serving a seven-year sentence for abuse of authority.