The central bank, which had not issued market stabilisation bills for about a week before Thursday's auction, said in a message to banks that bids must be backed by customer demand.

Nigerian banks have in the past chosen to invest in government debt rather than assume credit risk by lending.

It was unclear if the order applied to Thursday's auction only. Lenders can still purchase bills on the secondary market, traders said.

At Thursday's open market auction, the central bank offered 75 billion naira of bills, drawing demand totalling 475 billion naira for the various maturities. The bank sold one-year bill at a yield of 12.25pc.

A trader said Thursday's auction was targeted at non-bank investors, adding that the central bank has considered offering bills directly to foreign investors to support the currency.

Analysts say recent central bank policies aimed at boosting lending to help revive the economy could have a knock-on effect on the debt market and drive yields lower, to a point where they become unattractive to foreign buyers.