Nigeria devalues naira and raises rates after oil price slide
Nigeria has devalued the naira, saying a drop in oil prices had made it hard to defend its currency.
The country's bank central bank also raised interest rates from 12% to 13% in a bid to stem foreign reserve loses.
Nigeria has spent billions of dollars defending the naira using "dwindling foreign reserves", the bank's governor said.
Falling oil prices also affected the Angolan kwanza, which hit a record low against the dollar on Tuesday.
The bank's governor Godwin Emefiele said: "Falling oil prices have consistently reduced the accretion to external reserves, thus constraining the ability of the bank to continually defend the naira and sustain the stability of the naira exchange rate."
The bank moved the target band of the currency to 160-176 naira to the US dollar, compared with 150-160 naira previously.
It also raised interest rates by 100 basis points.
Nigeria, which has one of the biggest economies in Africa, and is one of the continent's leading energy producers, has spent billions of dollars in the past year shoring up the naira, Mr Emefiele said.
Foreign reserves stood at around $37bn (£23.5bn), down over 18% from a year ago.
"Big surprises from the central bank," said Razia Khan, head of Africa research at Standard Chartered.
"With these moves the central bank has shown absolute commitment to dealing with current challenges," she said. "They have not shied away from the tightening needed to sustain current FX [foreign exchange] reserves."
Meanwhile, Angola's kwanza traded traded as low as 100.895 against the dollar before recovering some ground to 100.700 on Tuesday.
Angola is Africa's biggest oil producer after Nigeria.