Italy's Eni and Shell bought the OPL 245 offshore field for about $1.3 billion in a deal that spawned one of the industry's largest corruption scandals. It is alleged that about $1.1 billion of the total was siphoned to agents and middlemen.

The Milan judge made the comment in handing down her reasons for the September conviction of Nigerian Emeka Obi and Italian Gianluca Di Nardo, both middlemen in the OPL 245 deal, for corruption.

"The management of oil companies Eni and Shell ... were fully aware of the fact that part of the $1.092 billion paid would have been used to compensate Nigerian public officials who had a role in this matter and who were circling their prey like hungry sharks," judge Giusy Barbara said in her reasoning.

She also said part of the money was given to some Eni managers.

Obi and Di Nardo have been tried separately from Eni and Shell, which also face corruption allegations over the same deal in a hearing that is expected to drag on for months.

Eni and Shell could not immediately be reached for comment.