Sources previously told Reuters that the 2019 "White Moon" shipment of crude oil, purportedly from Iraq, created panic within Eni over fears it could be, at least partially, Iranian.

Eni rejected the cargo, which it has said it bought from Nigerian firm Oando, who in turn bought the oil from the London branch of Italian fuel trading company Napag.

Handling Iranian oil would have breached sanctions the United States reimposed in 2018 after quitting a nuclear deal between Iran and world powers. 

The document from the Milan prosecutor's office, seen by Reuters, accuses a number of people of trying to defraud Eni with the shipment.

It names, among others, Massimo Mantovani in the capacity of former chairman of Eni Trading & Shipping (ETS), Francesco Mazzagatti as former partner and former director of Napag, and Boyo Omamofe as former chief of Oando Trading. Omamofe is currently named as deputy group chief executive on Oando's website.

A judge will decide in a closed preliminary hearing starting on Thursday and expected to last for several months whether there are grounds for a full trial.

Mazzagatti is now chief executive of Viaro, which took private London-listed North Sea oil producer RockRose in 2020.

A lawyer for Mazzagatti in Italy said his client was extraneous with respect to the Milan proceedings. A spokesperson for Mazzagatti in London described the Milan hearing as "procedural".

"(It is) related to false and outdated claims concerning a previous business that Mr Mazzagatti is no longer in any way associated with, either directly or through current business ventures. There has been no wrong-doing on his part," the spokesperson added.

Mantovani's lawyer said his client was innocent and that he would request the proceedings to move to the Italian city of Potenza on the grounds of "lack of territorial jurisdiction".

A lawyer representing Oando and Omamofe said he denied all wrongdoing, adding "If there was any deception, we too are deceived, not deceivers."

A spokesperson for Eni declined to comment.

(Reporting by Emilio Parodi in Milan, Shadia Nasralla in London; Editing by Kirsten Donovan)

By Emilio Parodi and Shadia Nasralla