Critics have also accused Sonangol -- which is both concession-granter and regulator of the industry -- of acting as a way to funnel part of the oil revenues to the political elite.
Martins responded to the criticisms by saying that "most" of Sonangol's revenues "are used to the wealth of our country and our people."
He added: "I would say all, depending on how you interpret it. Because what is our role? We have a production revenue, we put the production revenues on the hands of the minister of finance ... [it] goes through the hands of the government."
The Angolan government denies corruption in the oil sector. And recently, it announced a $5 billion sovereign wealth fund in a bid to diversify its economy, a move welcomed by lenders for its transparency. The state-owned investment fund, known as the Fundo Soberano de Angola, will invest domestically and internationally, focusing on infrastructure development and the hospitality industry.
At the same time, oil companies will soon be opening up new oil fields off Angola and the country hopes to become the largest producer of crude in Africa.
But with a history of corruption and problems of transparency, the biggest challenge will be ensuring that the profits filter down to ordinary Angolans.
Until then, many in the country say that only a tiny sliver of elites will truly benefit from Angola's oil.