JOHANNESBURG (Reuters) - South Africa's net gold and foreign exchange reserves fell by 0.5 percent to $32.973 billion in April, the first decline in almost two years, due to a sharp fall in the price of gold, central bank data showed on Friday.

Gross reserves decreased to $34.284 billion in April from $34.394 billion, the bank said in a statement posted on its Web site.

Net foreign currency holdings increased by $151 million to $30.8 billion, while gold reserves fell by $261 million to $3.484 billion.

"The gross reserves (number) is actually down and I think that's the first time in quite a long time. The main reason is obviously the fall in the gold reserves," Citadel economist Salomi Odendaal said.

The average gold price during the month fell to $871.60 an ounce from $936.95 in March.

Foreign exchange reserves increased by a relatively small amount given that the rand gained sharply against the dollar to 7.595 at the end of April from 8.10 previously.

"The forex reserves increase only by about $150 million, (so) it seems the Reserve Bank wasn't very active in the market this month," Odendaal said.

"It seems that they didn't want to prevent the rand from getting strong."

South Africa's central bank has said it will continue to build reserves to help cushion the country against external shocks, particularly with the current account deficit at 7.3 percent of GDP in 2007.

It brought a long-standing negative position in reserves into balance early in 2004 with the elimination of its loss-making forward foreign exchange book, historically the Achilles' heel of the currency.

While net reserves -- known as the net liquidity position -- have risen significantly over the past four years, they still lag holdings in other emerging economies.