Gabon, the sixth largest oil producer in Africa, has begun auditing oil producers in the country in what has led to unpaid tax claims, with oil executives saying the government is trying to aggressively increase earnings from operators.

“I think it is really driven by the desire to get a better deal for the state,” Reuters reports an anonymous oil executive as saying.

According to reports, executives who spoke to Reuters declined to be named for fear of jeopardising their interests in the country.

Gabon’s energy minister, Etienne Ngoubou acknowledged the government audited some oil operators in the country to verify if a contract was run in tandem with terms. “We got the opportunity to do some audits… we noticed a lot of exceptions,” he said.

“You engage in some negotiations with the operation company to check each exception and to agree if you have some tax (due),” he added.

According to report, three executives said Addax Petroleum, a subsidiary of China’s Sinopec, had been threatened with the loss of its Obangue onshore field in a disagreement over terms.

Ngoubou confirmed the dispute but cited unsustainable practices at the field, as the cause of the dispute.

“Their facility doesn’t respect the rules of the Institute of Petroleum … They have to fit with the specifications. Otherwise we take some decisions,” he said.

Other companies affected by the governments’ quest include Canadian Natural Resources and French groups Maurel & Prom and unlisted Perenco.

Gabon, formerly Africa’s third largest oil producer, lost output by a third of production since peaking at 370,000 barrels per day in 1997. The country has an estimated 3.7 billion barrels of oil reserves, leaving the country with several decades of crude oil wealth at current production level.