Central banks gold purchases in the third quarter were more than two times higher in comparison with the previous quarter, World Gold Council data showed on Thursday to the surprise of gold traders and analysts.

The scale of the buying, at 148.4 tonnes on a net basis, was far bigger than previously disclosed.

Central bank demand for 2011 may be the most since at least 1970, council data show.

Gold climbed to a record USD 1,921.15 an ounce in London on Sept. 6 and is heading for an 11th consecutive annual increase.

Holdings in bullion-backed ETPs yesterday were within 1 percent of the all-time high in August as concerns about Europe's debt crisis and slowing economic growth boosted demand. European bar and coin demand topped that in India or China, the council said.

The data came as a shock to traders and analysts, as it included a significant number of purchases that haven't yet been reported publicly, and whose buyers couldn't be identified due to confidentiality restrictions, the council said.

"This large number is a surprise," said UBS analyst Edel Tully told the Wall Street Journal. "This information is very bullish. And no doubt the market will be busy speculating on the identity of such buyers."