Ukrainian authorities have launched an investigation into whether former state officials paid Paul Manafort for political consulting work, the country's prosecutor-general says.

Yuriy Lutsenko told journalists in Kyiv on August 21 that Ukraine's State Fiscal Service opened criminal proceedings against ex-officials who served during Viktor Yanukovych's presidency and were suspected of paying Manafort for his work for Yanukovych and his Party of Regions.

Under Ukrainian law, state officials do not have the right to engage in business, Lutsenko said.

Lutsenko did not name any of the suspects, but at least six Ukrainian oligarchs and politicians, including four who held public office during Yanukovych's term, are alleged to have paid a total of $65.9 million to Manafort for consulting work, according to documents released by a U.S. court.

Three other cases related to Manafort's professional activities in Ukraine are currently being investigated by the country's Prosecutor General's Office. Manafort himself is not facing any charges in Ukraine.

The announcement of the new probe comes as the jury in Manafort's trial at the U.S. District Court in Alexandria, Virginia, entered its fourth day of deliberations.

Manafort, the former campaign chairman of U.S. President Donald Trump, faces 18 counts of tax evasion and banking fraud, with many of the charges centering on allegations that he illegally avoided taxes on some of the millions of dollars he earned from his political consulting work for Yanukovych and his party between 2010 and 2014.

If convicted, Manafort could spend the rest of his life in prison.

During his press briefing, Lutsenko cited the hundreds of documents presented by U.S. prosecutors in the trial and the testimony of one of its star witnesses, Manafort's former deputy, Rick Gates, as the reason behind the opening of the new investigation.

"There has been testimony that Manafort received funds for his consulting services for disgraced ex-President Viktor Yanukovych and the Party of Regions from specific politicians of Ukraine," Lutsenko said, according to the Interfax-Ukraine news agency.

Gates has testified in court that those who transferred millions of dollars to a Manafort account in Cyprus included Yanukovych's former chief of staff, Serhiy Lyovochkin; ex-Infrastructure Minister Borys Kolesnikov; former National Security Council Secretary Andriy Klyuyev; and lawmaker Serhiy Tihipko.

None of the men could immediately be reached for comment.

"Therefore, we opened a criminal case into possible violations of these state officials at that time," Lutsenko said, adding that the State Fiscal Service "will obviously work with those jurisdictions in the territory of which there are mainly offshore companies mentioned during Manafort's trial."

Lutsenko conceded that the investigation will be a slog but said investigators would see it through.

"If it is proved" that any civil servant provided funds to Manafort, he said, "then he will be held liable in accordance with current Ukrainian legislation."