The RBI has lifted a three-year ban on Tamilnad Mercantile Bank's branch opening with effect from October 21, the lender said on Friday. This development comes after the Thoothukudi-based bank's shares were listed on the stock exchanges on September 15. Currently, it has 509 branches, of which 106 are rural, 247 are semi-urban, 80 are urban and 76 are metropolitan.