Spot gold soared to an all-time high above $1,910 on Tuesday, scoring a record top for a fourth consecutive session, as persistent worries about global economic growth burnished bullion's safe-haven appeal.

The precious metal was headed for a seventh straight session of rise and a monthly gain of more than 16 percent, highest since September 1999.

Spot gold gained 0.8 percent to strike an unprecedented $1,911.46 an ounce, before easing to trade flat at $1,897.05 by 2:26 a.m. EDT.

U.S. gold rose 1.4 percent to a record high of $1,917.90, and retraced to $1,900.80.

Investors are waiting for flash purchasing managers' index (PMI) data for Germany, France and the euro zone later in the day, with a weak number likely to exacerbate fears about bailing out the bloc's indebted peripheral states.

We are not hearing much good news out of Europe or the United States, said Darren Heathcote, head of trading at Investec Australia.

The picture looks pretty bleak in the short term... For the time being investors are happy looking at gold as safe haven in these troubled times, and will continue to do so until we see something positive and sustainable.

On the chart, gold has been in the overbought territory since early August, with the Relative Strength Index hovering about 83.

Technical analysis suggested gold could pull back to $1,860 during the day, said Reuters market analyst Wang Tao.

SGE RAISES MARGINS, TRADING LIMITS; EYES ON COMEX

The Shanghai Gold Exchanges said it will raise trading margins on three of its gold spot deferred contracts to 12 percent from 11 percent starting August 26, and widen the daily trading limits to 9 percent from 7 percent.

Shanghai gold T+D contract fell less than 2 yuan from a high of 391.85 yuan per gram at the news, but has since stabilized around 391 yuan, or $1,900.02 an ounce.

Traders are eyeing potential hikes in U.S. gold futures margins. They were last raised on August 11 by 22 percent, triggering a correction in gold prices.

But concerns about the world's economic growth soon offset the impact of the margin hike, and gold embarked on another leg of record-setting rally just a week later.

Everyone says that gold has been rising too fast, beware, beware, beware! said Ronald Leung, a physical dealer at Lee Cheong Gold Dealers in Hong Kong. But there is no sign of gold prices turning to point south.

Leung said scrap selling was minimal and sellers are waiting for higher prices, while investors continued to show buying interest.

Market participants are eyeing an annual central bank conference in Jackson Hole, Wyoming, where the U.S. Federal Reserve Chairman Ben Bernanke is scheduled to speak on Friday.

Spot silver rose to $44.14, its strongest since early May, tracking gold's strength. It was later trading at $43.44, down 0.7 percent from the previous close.

Spot platinum hit a three-year high at $1,912 an ounce, before easing to $1,904.24.

In other news, China's flash Purchasing Managers' Index, designed to preview the country's factory output before official data, edged up to 49.8 in August, from July's final reading of 49.3.

That leaves the index a touch under the 50-point mark that demarcates expansion from contraction in activity. HSBC publishes its final China PMI index for August on Sept 1.

(Editing by Himani Sarkar)

Germany China Ben Bernanke Gold