The CME Group, the world's largest commodities exchange, raised its margin requirement on trading 100-ounce gold futures by 21.4 percent, the third rise since July.

Coupled with the two previous hikes, both in August, margins have risen by $5,400 -- nearly 90 percent.

The raise in margins came after gold slumped more than 6 percent at one point, registering its third-sharpest daily loss in the past 20 years, its biggest slide since the financial crisis in 2008.

Gold fell more than $100 on Friday as a slide turned into a free fall, with weeks of volatility, renewed strength in the dollar and talk of hedge fund liquidation wrecking its safe-haven status.U.S. gold futures' benchmark December contract on COMEX settled down 6 percent, or more than $101, at under $1,640 an ounce.

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