The Financial Supervisory Agency is stepping up pressure on 13 domestic and foreign banks to review their lending policies toward "shoko" lenders, financial sources said Thursday.

The agency started interviewing officials of the banks the same day on their firms' dealings with the lenders, urging them to submit relevant documents.

The banks are under increasing pressure to reduce or stop providing funds to the lenders, which are being criticized for their alleged strong-arm loan-collection tactics that sometimes border on extortion.