In a notification, the RBI said while granting advance against the security of specially minted gold coins sold by banks, state/central co-operative banks "should ensure that the weight of the coin(s) does not exceed 50 grams per customer'.
Also the amount of loan to any customer against gold ornaments, gold jewellery and gold coins (weighing up to 50 grams) should be within the Board approved limit, it added.
Earlier, similar restrictions were imposed on commercial banks.
The RBI's latest move comes in the backdrop of government raising import duty on gold to 8 percent from 6 percent.
The central bank has also advised banks not to sell gold coins, Finance Minister P Chidambaram said yesterday.
RBI has also imposed restrictions on gold imports by banks.
Surge in gold imports has become a cause of concern for both the government as well as the RBI as it putting pressure on the current account deficit, which is likely to be around 5 percent of the GDP in 2012-13.
In the first two months of the current fiscal there has been significant spurt in gold imports as the average foreign buy of the precious metal stood at 152 tonnes in April and May. The monthly average import in 2012-13 was 70 tonnes.