Dutch oil trader Vitol said Tuesday it spent around $27 million to take on a majority stake in the refining business held by Nigerian energy company Oando.

Vitol and Africa-focused private investment firm Helios Investment Partners said it was taking on a majority stake in the downstream, or refining side, of the Nigerian company.

"This investment is a further reflection of our confidence in the Nigerian economy, and will be independent of the services we provide to our long standing Nigerian customers," Vitol President and Chief Executive Officer Ian Taylor said.

A World Bank report finds lingering conflict in Nigeria, stemming largely from the Boko Haram insurgency, is constricting the nation's economy. The threat to the economy "disappears" in forecasts once an amnesty is extended to militant groups operating in oil-producing regions in Nigeria, the bank said.

Vitol said the new entity will function as a standalone company led by local management overseeing 400 retail service stations with an estimated 84,000 tons of storage capacity. A complementary business extends to the Ghanaian market.

Controlling 12 percent of the Nigerian market, the new business structure will be the second largest of its kind in the country.

Revenue for Vitol fell to its lowest level in four years. The company said it handled 268 million tons, or around 1.9 billion barrels of oil equivalent, last year, down nearly 3 percent from the previous year.

Vitol said the new business entity will likely retain the Oando brand. As of 2013, Oando had revenues of more than $2.5 billion.