The long-running graft case revolves around the purchase of the Nigerian OPL 245 offshore oil field in 2011 for about $1.3 billion. Prosecutors allege that about $1.1 billion of that was siphoned off to politicians and middlemen.

At a public hearing, prosecutors asked the court to accept two emails sent to Italy by UK authorities. The emails originate from a separate London court case launched by the Nigerian government against JPMorgan Chase, claiming over $1.7 billion for its role in the disputed oilfield deal.

The first is an email sent by former Nigerian Attorney General Mohammed Adoke Bello to JPMorgan from the email address of a company owned by Aliyu Abubakar - a Nigerian oilman whom prosecutors allege paid $500 million in cash as part of a bribe.

In this email, seen by Reuters, Adoke sent the bank copies of the resolution agreement regarding the oilfield acquisition.

The prosecutors said they considered it relevant to establish the relationship between Adoke and Abubakar.

Adoke was charged last year for allegedly receiving bribes to facilitate the deal, and he pleaded not guilty to all charges.

Abubakar's trial will start in coming weeks in Milan. He denies any wrongdoing.

The second email, also seen by Reuters, is between two JPMorgan officials expressing doubts about transferring $1.1 billion to two accounts at Nigerian banks.

Milan magistrates said at Wednesday's hearing they considered the email significant as it shows there were doubts within the bank over the transfer, which a Swiss and a Lebanese lender had previously refused to carry out.

The Milan court will decide on Feb. 3 whether to admit the two documents in the case.

JPMorgan declined to comment. It is not part of the Milan case.

The companies and defendants involved in the Milan case, including Eni's current CEO Claudio Descalzi, have all denied any wrongdoing.

Milan prosecutors have asked for jail sentences for all the defendants and fines for the two oil giants.

On Wednesday lawyers for Eni and Shell asked for the companies to be acquitted.

The verdict is expected at the end of March.

(Reporting by Emilio Parodi and Alfredo Faieta, editing by Stephen Jewkes, Kirsten Donovan)