MADRID, May 30 (Reuters) - Spanish bank Santander said on Wednesday it would increase a commercial paper issue aimed at retail investors to 15 billion euros ($18.6 billion) at a time when wholesale financial markets are practically shut for Spanish lenders.
The bank has progressively increased the size of the planned issue over the last months from the original amount of between 5 billion and 7.5 billion euros announced in September.
Spanish banks are struggling to capture deposits and most of them heavily rely on cheap money from the European Central Bank (ECB).
According to an original filing in September to the Spanish stock market regulator, commercial paper, which is being sold to retail clients, offered an interest rate of between 3 percent and 3.75 percent depending on maturity.
However, in Wednesday's filing to the securities regulator the bank did not state the rate. ($1 = 0.8069 euros) (Reporting by Jesús Aguado; Editing by Will Waterman)