The Russian government has asked Italy to be "reasonable" over a Russian citizen caught up in a Nigerian graft case in Milan and drop the charges against him, according to legal documents seen by Reuters.

Ednan Tofik ogly Agaev, a former Russian ambassador in Colombia, is charged with international corruption in a case revolving around the 2011 purchase by oil majors Eni and Shell of Nigeria’s OPL 245 oilfield.

Milan prosecutors allege bribes totaling around $1.1 billion were paid to win the license to explore the field.

Agaev and all the parties involved in the case have denied any wrongdoing.