SOFIA, Bulgaria (AP) — The U.S. government on Wednesday sanctioned six Bulgarian public officials and businessmen, as well as their networks encompassing 64 entities, for their allegedly “extensive” roles in corruption.

The State Department announced the public designation of former public officials Alexander Manolev, Petar Haralampiev, Krasimir Tomov, and Delyan Peevski, as well as current official Ilko Zhelyazkov.

In Sofia, Bulgarian interim Prime Minister Stefan Yanev said he was informed about the act by U.S. Under Secretary of State for Political Affairs Victoria Nuland by telephone.

The sanctions on the people and companies effectively prevent them from accessing the U.S. financial system, freeze any of their U.S. assets and bar Americans from dealing with them.

European Union member Bulgaria has repeatedly been reprimanded by Brussels for a lack of efforts to effectively fight corruption, and the Transparency International watchdog has declared it the most corrupt country in the EU.

In their official capacities, Manolev, Haralampiev and Tomov were allegedly involved in corrupt acts that undermined the rule of law and the Bulgarian public’s faith in their government, including by using political influence and official power for personal benefit, the state department said in a statement.

It added that Peevski, in his capacity as a member of parliament, allegedly used Zhelyazkov, an official in the National Bureau for Control on Special Intelligence-Gathering Devices, “as an intermediary and accomplice to peddle influence and pay bribes to protect himself from public scrutiny and to exert influence over key institutions and sectors in Bulgarian society.”

The U.S. Department of the Treasury also has designated Peevski, Zhelyazkov and Bulgarian oligarch Vassil Bojkov, along with 64 entities owned and controlled by Bojkov and Peevski, for their alleged roles in public corruption. It said the move was its single biggest action targeting corruption to date.