Viktor Pshonka said on January 18 that Tymoshenko has been notified that she is suspected of having ordered the killing of Ukrainian businessman and legislator Yevhen Shcherban.
He said investigators have found enough evidence that Tymoshenko, together with former Ukrainian Prime Minister Pavlo Lazarenko, ordered Shcherban's slaying.
"The order was to kill Shcherban by any means," Pshonka said. "What are the reasons for this killing? Profit-seeking business interests. Lazarenko and Tymoshenko's plans did not coincide regarding the business, where Shcherban did not want to subordinate his business to the UES," he said in a reference to the gas company that Tymoshenko headed in the 1990s, United Energy Systems of Ukraine.
He also claimed Tymoshenko and Lazarenko paid $2.8 million for the murder of Shcherban, who was shot dead at an airport in eastern Ukraine in 1996.
Tymoshenko and Lazarenko both deny the accusations.
Tymoshenko's defense lawyer, Serhiy Vlasenko, rejected the new accusations as absurd in a telephone interview with RFE/RL's Ukrainian Service.
"That has nothing to do with the law," Vlasenko said. "They could have submitted a clean piece of paper on which they could have written that 'Yulia Tymoshenko killed President [John F.] Kennedy.'"
Her lawyer said the prosecutor-general's announcement was likely linked to a ruling on Tymoshenko's appeal by the European Court of Human Rights that is expected early this year.
"They do not do anything by chance," Vlasenko said. "I am convinced that they did this on the eve of the European court ruling, understanding that the decision of the European court will be simply crushing for them."
Tymoshenko was convicted in 2011 of abuse of office and sentenced to seven years in prison.
She says the trial was a political vendetta by Viktor Yanukovych, who was initially defeated after a flawed election that sparked the so-called Orange Revolution in 2004-05 but returned to defeat Tymoshenko in a 2010 presidential election.
Western governments and human rights groups have criticized the trial as politically motivated.
Tymoshenko is also facing a second trial for alleged tax evasion and embezzlement when she headed the UES.
That trial was adjourned on January 18 until February 12 because she did not appear in court due to health problems.
Earlier in the day, Vlasenko said Tymoshenko's health had deteriorated to a "critical" level.