A rare 5.16-carat blue diamond sold at auction for $6.4 million in Hong Kong confirming Asia's fast-growing taste for the precious stone.

London's famed Moussaieff Jewellers paid more than the $5.9 million expected price tag for the pear-shaped stone, the first blue diamond from the celebrated De Beers Millennium Jewels Collection.

"The price was above the high estimate," a spokesman for auction house Sotheby's. But the world per-carat record for a blue diamond remains the $10.5 million paid by a Hong Kong property tycoon for a seven-carat blue diamond in Geneva in May last year.

In December, a five-carat chickpea-sized vivid pink gem set a per-carat world record price for a diamond when it fetched $10.8 million at an auction in Hong Kong.

This week's collection, displayed in London's Millennium Dome in 2000, consists of 11 high-quality blue diamonds from the Premier Diamond Mine of Transvaal, South Africa.

It was reported that the mine could produce only one blue diamond of such high calibre each year.

Sotheby's said gem sales in Hong Kong were on the rise - the city has overtaken New York to become the company's second biggest market after Geneva.

Terry Chu, deputy head of Sotheby's jewellery department for China and Southeast Asia, said diamonds were particularly appealing to new Asian buyers because of their stable prices and assured quality.

"There have been a lot of new diamond buyers from mainland China, Hong Kong, Singapore, Taiwan and elsewhere in the region," Mr Chu . "I think after the financial crisis, the Asian buyers realised that the prices of diamond are relatively stable compared to other types of auction items," remarked Mr Chu.

According to Sotheby's, Hong Kong has become the world's third largest auction hub after New York and London, spurred by China's growing wealth and increasing taste for fine art.