(Reuters) - Gold and silver prices slid on Thursday, with silver tumbling more than 6 percent, as renewed strength in the dollar and concerns over the outlook for economic growth sparked broad-based selling of commodities. Spot gold was bid at $1,481.96 an ounce at 0952 GMT against $1,499.75 late in New York on Wednesday, having earlier hit a low of $1,481.85. Silver fell to a low of $32.88 and was later at $33.04 an ounce against $35.06. Gold dropped more than 1 percent on Wednesday and silver nearly 9 percent as hefty gains in the dollar prompted selling across commodities. They extended those losses as the dollar hit a fresh three-week high against a basket of major currencies on Thursday, while concerns over the financial health of some smaller euro zone economies kept the euro under pressure. Dollar strength makes assets priced in the U.S. unit, like commodities, more expensive for other currency holders. "External factors are playing the most important role here -- the firmer dollar, and secondly somewhat weaker equity markets which reflect higher risk aversion among market players at the moment," said Commerzbank analyst Daniel Briesemann. "Given that commodities still show quite good price performance over the last 12 months and are still in positive territory, some market players are taking profits to cover losses elsewhere," he added. Oil slipped 1.3 percent and base metals like copper and aluminum declined, as buyers of industrial commodities worried about the outlook for economic growth from major consumers China and the United States. Expectations that China will continue to raise interest rates to combat inflation is fuelling fears that the country's burgeoning demand for raw materials may ease. Higher rates and a consequent lessening of inflation fears may also weigh on gold. SILVER VULNERABLE Gold prices have dropped more than 5 percent and silver by nearly a third from the record highs they hit in recent weeks. Silver is underperforming gold after strongly outperforming it in the first quarter's rising market. The world's largest silver-backed exchange-traded fund, the iShares Silver Trust, reported an outflow of more than 45 tonnes on Wednesday. Its holdings have declined by more than 480 tonnes since the end of April. Increases in the amount of money exchanges require to trade silver have rattled futures markets, meanwhile. Speculators have liquidated long positions in silver in both New York and on the Shanghai Gold Exchange in recent weeks, pressuring the metal. "While the long silver trade is a lot less crowded than it was earlier this month, news that the SGE will raise initial margins on the metal to 19 percent, from 18 percent, and widen the allowed daily range to 13 percent - both effective tomorrow - may spook those investors who are still long that further margin hikes will follow," said UBS in a note. "The only thing we can be certain of in silver right now is that the roller coaster journey is going to continue for some time." The gold:silver ratio -- the number of ounces of silver needed to buy an ounce of gold -- rose toward 44 on Thursday, having slipped to 31.7 in late April, its lowest in 28 years. From a technical perspective, it is finding support around current levels, but remains vulnerable. Among other precious metals, platinum was at $1,751.49 an ounce against $1,770.10, while palladium was at $702 against $701.50. (Reporting by Jan Harvey; Editing by Alison Birrane)

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