Blackstone and Apollo are among the private equity groups that are considering bids for the unit sold by CatalunyaBanc, according to sources close to the deal. CatalunyaBanc, a Barcelona-based lender, is one of the banks the government of Spain bailed out last year. The bail out move followed reports that the bank had taken in substantial losses in real estate.

The planned sales showcase how Spanish banks are willing to exit their worst property loans. Banks in the country have been under increasing pressure by regulators to exit some of its assets and to find ways in boosting regulatory capital. Most Spanish banks have deferred the move to do so because some of the measures meant taking on even more losses.

Other banks have also started seeking buyers for a section or for all of their units that handle their struggling property assets. Among these banks are La Caixa, the operator of Spain's third largest bank and Bankia, the nationalised bank that acquired close to EUR25 billion in European aid.

"It's the first step by Spanish banks in bringing those distressed assets to market," KPMG Portfolio Solutions Group director, Andrew Jenke, stated.