US oil field services firm Halliburton has begun an internal investigation into its operations in Iraq focusing on payments made to third parties.

The payments relate to customs and visas in Iraq, as well as the company’s operations in Angola, according to a filing to the Securities and Exchange Commission (SEC) on 27 July.

“We expect to continue to have discussions with the DOJ [Department of Justice] and the SEC regarding the Angola and Iraq matters described above and have indicated that we would further update them as our investigations progress. We have engaged outside counsel and independent forensic accountants to assist us with the investigations,” says the statement.

The US firm has won a number of service contracts at oil fields in Iraq. Among other drilling contracts, the firm was awarded a deal in April 2011 for the refurbishment of wells in the West Qurna Phase-one oil field in the south of Iraq, which is being developed by the US’ ExxonMobil.