Tanzania, May 23 -- Nigeria has received its first sovereign credit rating upgrade in 14 years, with global ratings agency S&P Global Ratings citing the growing impact of billionaire Aliko Dangote's $20 billion refinery as a major factor behind the improvement.

S&P upgraded Nigeria's long-term sovereign rating from B- to B on May 15, saying the refinery has helped reduce the country's dependence on imported fuel, strengthen foreign exchange reserves and improve its external financial position.

Located near Lagos, the refinery is operating close to its 650,000 barrels-per-day capacity and is increasingly supplying fuel, gas and fertiliser to the domestic market.

According to S&P, this has helped cushion Nigeria from global supply disrup...