The central bank (CBN) last year injected $4 billion into nine lenders deemed to be so weakly capitalized that they posed a systemic risk to sub-Saharan Africa's number two economy. It has said it wants new investors to recapitalize them.

Parliament has passed legislation to create an asset management company (AMCON) to soak up bad loans at the troubled banks in exchange for government bonds, in a bid to clean up their balance sheets and make them more attractive to investors.

But while potential investors have been doing due diligence on the rescued banks, financial industry sources say it is unclear whether all of them will find the capital injection they need.

Central Bank Governor Lamido Sanusi met with the management and shareholders of the rescued banks on Thursday, telling them that having secured depositors' funds the focus was now to salvage some value for shareholders.

"Sanusi noted that liquidation and nationalization are not desired options, stating that he is convinced that fresh injection of capital through strategic partnership remains the best approach," the CBN said in a statement.

"However, he cautioned that should the ongoing process to recapitalize the banks be frustrated, the CBN would have no other option than to go for liquidation as provided for by the existing legal framework," it said.

Some shareholders have challenged the central bank's right to effectively sell the bailed out banks, which include Afribank , Intercontinental Bank, Oceanic Bank and Union Bank.

Sanusi said the CBN was not itself selling the banks but had merely recommended financial advisers who were working with management to try to source fresh capital.

"The CBN will not usurp the rights of shareholders ... and shareholders should rest assured that the final decision on the recapitalization of the banks rests with them," the CBN said.