Nigeria naira weakened to a 22-week low against the US dollar on the interbank on Tuesday, following strong demand for the greenback that the central bank could not meet at its foreign exchange auction the previous day, traders said.

The naira eased to 163.68 against the dollar on volatile trades at the interbank market on Tuesday. It had closed 162.95 naira to the greenback on Monday.

The central bank sold $300 million at 155.90 naira to the dollar on Monday, without meeting demand for the US currency, dealers say, and lower than the 155.85 naira it sold the greenback at its last auction on Wednesday.

The bank did not disclose the amount of dollar demand at its window.

“The demand for the US dollar is not being met at the central bank window. So we have all the oil importers as well as foreign investors exiting short term government securities exerting pressure (on the naira),” one dealer said.

“These two pressures are basically why the naira is weakening,” he told Reuters.

Stuart Culverhouse, a chief economist at London-based brokerage firm Exotix, said heightened risk aversion across global markets and concerns about global growth particularly in the Eurozone, meant foreign investors were pulling out from frontier markets into safe havens.

“Nigeria has been impacted ... that has caused some investors to exit the T-bill market,” he said, adding that his firm had a buy recommendation on Nigeria 6-month treasury bills yielding 16 percent.

Proceeds from oil sales, which go through the central bank, are the main source of dollar liquidity in Africa's second-biggest economy. Foreign oil firms operating in the country also sometimes exchange dollars at the interbank for naira to run their day to day operations. - Reuters