The European Central Bank cautioned on Wednesday against speculation over the outcome of its stress tests after a media report said at least 11 banks had failed the landmark financial health checks, driving some banking shares lower.

Austria's Erste Group rejected the report from Spanish newswire Efe, which said that it along with banks from Italy, Belgium, Cyprus, Portugal and Greece, had failed the ECB review based on preliminary data, but it gave no details of the size of the capital holes at the banks.