The government of Nigeria is suing Royal Dutch Shell Plc, Eni SpA and other companies for more than $1 billion over a 2011 oil deal it says was tainted by corruption.

The suit, filed Wednesday in London, alleges that money the companies paid to acquire an oil exploration license in the Gulf of Guinea was diverted to bribes and kickbacks, the Nigerian government said in a press release. The transaction is already the subject of a separate, ongoing criminal trial in Milan.

Shell, Eni Face $1.1 Billion Nigerian Lawsuit Over 2011 Deal

Nigeria’s government claims that Shell and Eni are partly responsible for the behavior of “corrupt Nigerian officials” who used a $1.1 billion payment to acquire the oil block for personal enrichment. The suit seeks to recoup that money, which it says belongs to the Nigerian people.

Nigeria’s federal government is already a civil party in the case in Milan, and can seek damages from that court. Additionally, it sued JPMorgan Chase & Co. in London last year, accusing it of failing to prevent the illicit transfer of funds related to the transaction. The bank said the claim was without merit.

Shell and Eni have previously denied any wrongdoing in the criminal case over the block, called OPL 245, that is under way in Italy. They said they made the payment into a legitimate government account to settle legal claims related to the block.

Shell, Eni Face $1.1 Billion Nigerian Lawsuit Over 2011 Deal

A spokesperson for Shell reiterated the company’s payments in Nigeria over OPL 245 were legitimate and said since the matter is being tried in Milan “it would not be appropriate for us to comment in detail on the new claims that have been made.” A spokesperson for Eni said it confirmed “the correctness and compliance of every aspect of the transaction in respect of OPL 245” and rejected “any allegation of impropriety or irregularity.”

The Nigerian government also included Nigeria-based Malabu Oil and Gas in the lawsuit, and a company called Energy Venture Partners Ltd. Malabu was allegedly controlled by Nigeria’s former Petroleum Minister Dan Etete, who took possession of the $1.1 billion payment and used it for bribes and kickbacks, according to the lawsuit.

A lawyer for Etete that is representing him in the Milan trial said he was unaware of the case in London and was unable to immediately comment.