Italian major Eni said the US Department of Justice has closed an investigation into its business practices in Algeria and Nigeria without taking any action against the company.

"Eni reiterates that neither the company nor its management was involved in any alleged corrupt activities in relation to the OPL 245 transaction in Nigeria," the company said in a statement.

"Today’s decision by the DOJ confirms the findings of independent advisors, who conducted investigations into the claims following the decision taken by Eni’s controlling bodies, which also found no illegal activity."

The company also said it was "confident that the allegations currently put forward before the Court of Milan will be found to be groundless."

In March 2018 Eni, as well as Anglo-Dutch supermajor Shell, submitted internal investigations to the US Department of Justice and US Securities & Exchange Commission on the acquisition of a major oilfield in Nigeria that has drawn allegations of graft and triggered legal proceedings in Italy, Nigeria and the Netherlands.

Italian prosecutors allege that bribes were paid to secure the block, a charge that the companies have fiercely disputed with both denying criminal wrongdoing.

Both companies are listed in the US and accordingly the voluntary filings were seen as a push to make authorities aware of the pending issue which the US could consider for prosecution under the US Foreign Corrupt Practices Act, Reuters reported at the time.

A trial in Milan against the companies is still pending, and could continue for years.

In December that Italian court found that Eni and Shell were aware that funds paid in 2011 to acquire deep-water Block OPL-245 in the Niger Delta from Nigerian company Malabu Oil & Gas were lining the pockets of key officials involved in the transaction.

A Milan court previously ruled that two middlemen, Nigerian Emeka Obi and Italian national Gianluca Di Nardo, were guilty of corrupt practice and sentenced both to four years in jail.

The case against Obi and Di Nardo was separated off from the main trial for reasons of expedition and the court is not expected to conclude the main process until next year.

The Global Witness anti-corruption advocacy group issued a statement on the news.

"We look forward to the DOJ outlining their reasons for this decision. It remains the case that Eni and its most senior executives are currently on trial in Italy for allegedly bribing Nigerian politicians for access to a lucrative oilfield," GW campaigner Barnaby Pace said in a statement.

"The alleged scheme came less than a year after the company had sworn it would clean up its act after admitting to paying bribes in separate Nigerian oil deals. If the company is found to have reoffended it should face serious penalties in the United States and other jurisdictions in which it operates.”