The Rs 12,600 crore fraud-hit Punjab National Bank on Thursday clarified that the Reserve Bank of India (RBI) had done risk-based supervision of the bank on an annual basis."There have been reports in a section of media that Reserve Bank of India has not conducted any audit at Punjab National Bank Brady House, Mumbai branch since 2009. It may be clarified that RBI does risk based supervision of the bank on annual basis," the bank said through its twitter handle.PNB, the second largest public sector bank in India, is in the eye of storm after Rs 12,600 crore fraud was detected involving diamond trader Nirav Modi and owner of Gitanjali Gems, Mehul Choksi.Following the multi-crore fraud the PNB appointed A.K.Pradhan as Group Chief Risk Officer, a regulatory filing by the bank said here on Tuesday.Earlier, the fraud amount was said to be Rs 11,3000 crore, but onn Tuesday, the bank had informed the stock exchanges that additional amount of Rs 1,300 crore had been discovered to be part of the fraud. On Tuesday Firestar Diamond Inc, the US company of Nirav Modi had filed for bankruptcy in a New York court, under chapter 11.