A rights group says Angola must account for $32 billion in missing government funds thought to be linked to the state oil company.

Human Rights Watch, citing a report by the International Monetary Fund, says the money was spent or transferred between 2007 and 2010 without being properly accounted for in the budget.

The sum is equal to almost 30 percent of Angola's annual gross domestic product.

The IMF report said some of the discrepancy may be connected to the flow of funds into foreign escrow accounts, beyond what can be explained by Angola's debt service obligations.

It also said state oil firm Sonangol may be understating the funds it receives.

The IMF said it is holding discussions on the matter with Angolan authorities, and that a financial reconciliation process is underway.

Angola is Africa's second-biggest oil producer behind Nigeria. Human Rights Watch has accused the government of mismanaging and losing oil money before, but later reported the country had improved its financial reporting system.

The rights group has also accused the government of not addressing economic inequalities in the country and using force to suppress demonstrations against President Jose Eduardo dos Santos, who has ruled Angola since 1979.