The bank said the ban was meant to discourage speculative gold purchases. Borrowing could continue for gold purchases for jewelers, however, the banks said.
Gold added $4.90 or 0.28 percent to reach $1,728.50 per troy ounce on the Comex division of the New York Mercantile Exchange, rising for the second consecutive day.
Silver nudged higher, closing up 43 cents or 1.3 percent to $33.45 per ounce.
The dollar index was flat. The euro rose to $1.283 from Tuesday's $1.2818. Against the yen, the dollar rose to 82.52 yen from 81.69 yen.