(Adds detail, comments)
MILAN, July 4 Italian prosecutors have opened a probe into alleged corruption relating to the 2011 acquisition of a big oil field in Nigeria by Italian oil group Eni and Shell, judicial sources with direct knowledge of the matter said on Friday.
The sources said the investigation related to alleged international corruption surrounding the purchase of the block.
Eni confirmed the investigation and said in response to a Reuters' request for comment: "Eni declares the absolute properness of its handling of the dealings in question and assures its full cooperation with Italian prosecutors."
The probe relates to the purchase of offshore oil block OPL 245 in Nigeria. Last year, British police began investigating a money-laundering allegation in connection with the same field.
Italian daily Il Fatto Quotidiano said on Friday police had visited Eni offices last Wednesday to notify the company it was being investigated and to ask for documents.
In response to Il Fatto's article, Eni confirmed it had received notice of the probe and said it had done no wrongdoing.
The concession for OPL 245, which industry sources have said could contain up to 9.23 billion barrels of crude, was awarded to Eni and Shell by the Nigerian government in 2011 for $1.3 billion.
At that time, Nigeria said it was helping to resolve an ownership dispute over the block between Shell and Malabu Oil and Gas company and immediately transferred $1.09 billion from the sale to Malabu.
"No commercial agreement was reached by Eni with the Malabu company that previously owned the block in question," Eni said, adding it had paid the amount into a current account of the Nigerian government.
The judicial sources said Shell was not under investigation by the Italian authorities because the company is in a different jurisdiction.
Shell declined to comment on the Italian investigation. A Shell spokesman said of the OPL 245 deal: "Shell companies have acted at all times in accordance with both Nigerian law and the terms of the OPL 245 resolution agreement with FGN (Nigerian government). We are open and transparent about all payments made by Shell companies to the FGN and how much they were."
(Reporting by Stephen Jewkes. Editing by Jane Merriman)