Angola's justice minister says the country has so far this year recovered more than $5bn (£3.8bn) stolen from the state.Francisco Queiroz said this included $3bn siphoned off from the sovereign wealth fund.He said some countries were obstructing Angola's efforts to track down the looted funds.The son of Angola's former President Jose Eduardo dos Santos, who headed the sovereign wealth fund is on trial for corruption. Jose Filomeno dos Santos denies the charges.Angolan President Joao Lourenco has vowed to crack down on the country's massive corruption problem.