Nigeria's downstream oil regulator has alleged ExxonMobil Corp was involved in the illegal lifting of petroleum products from an offshore terminal, according to a letter of complaint to the petroleum ministry seen by Reuters.

Exxon denied the accusation, saying in an emailed response that its "operations are carried out in full compliance with the law".

Nigerian Midstream and Downstream Petroleum Regulatory Authority (NMDPRA) said in the letter that Barumk Gas, a shipping vessel, was lifting butane from the ExxonMobil-controlled Bonny River Terminal without its "authorization or participation".

According to the law, the regulator is the only one allowed to have a key to the oil valve and companies need to be accompanied by a member of the regulatory staff to tap the oil.

"The actions of ExxonMobil and Barumk Gas constitute economic sabotage, criminal damage and theft of Nigeria's national resources," NMDPRA Chief Executive Farouk Ahmed said in the letter dated June 8.

He said Barumk Gas should be stopped from sailing out until an investigation was conducted.

Refinitiv data showed Barumk Gas was fully loaded at the Bonny Terminal.

The Petroleum Ministry and NMDPRA did not respond to requests for comment.

In November last year, a Nigerian court charged 26 men with conspiracy to commit a maritime offence and attempting to illegally deal in crude oil after authorities accused their supertanker of sailing in Nigerian waters without authority.

Oil majors in Nigeria have in the past been forced to halt output following the illegal tapping of pipelines.

Reuters