Gold futures climbed above $600 an ounce Thursday morning to trade near their highest level in three weeks with the return of the precious metal's allure as a defensive investment measure in the face of strength in oil prices and weakness in the U.S. dollar.

"Gold continues to build a base after absorbing strong bouts of selling," said Peter Grandich, editor of the Grandich Letter.

"A close above $610 is needed to turn the market technically bullish again and that appears to be only a question of when," he said.

Gold for December delivery climbed $9.40 to $602 an ounce on the New York Mercantile Exchange, after rising as high as $604. The contract hadn't traded above $600 since Oct. 2.

December silver rose by 30 cents, or 2.5%, to stand at $12.12 an ounce.