Gold futures surged the most in two years as weakness in the U.S. dollar boosted the investment appeal for the precious metal, causing prices to lift nearly 4 percent.

Gold futures for August delivery jumped $32.80, or 3.7 percent, to $915.10 an ounce on the Comex division of the New York Mercantile Exchange. The contract hit an intra-day high of $916.50, its highest level since May 27.

The Fed yesterday kept its benchmark interest rate at 2 percent, even as policy makers acknowledged heightening inflationary expectations.

The dollar index , which tracks the performance of the U.S. dollar against a basket of other major currencies, was at 72.55, compared with 72.90 in late North American trading Wednesday, following the Fed's announcement.

An OPEC official said crude oil may reach $170 a barrel soon. Crude-oil futures climbed to a new record high of $140.05 a barrel in electronic trading on Globex Thursday, boosted by a weaker dollar and output level concerns.

Silver futures for September delivery soared 61.3 cents, or 3.7 percent, to $17.22 an ounce, the biggest gain since June 16. Silver has advanced 39 percent in the past year, while gold climbed 42 percent.

Also on the Nymex, July platinum surged $55.30 to end at $2,068.80 an ounce.September palladium gained $6.25 to finish at $471.25 an ounce and September copper rose 6 cents to $3.83 a pound.