HONG KONG (AFP) - A flawless fancy vivid pink diamond sold for a record US$17.7 million (S$22 million) in Hong Kong late Tuesday, Sotheby's said.

Mr Quek Chin Yeow, deputy chairman of Sotheby's Asia, said the pear-shaped 8.41-carat stone has set a world auction record for a fancy vivid pink diamond.

The buyer's identity was not immediately disclosed.

Internally flawless clarity is extremely rare in pink diamonds, and the auction house said this, in combination with its "fancy vivid" colour grading, made the stone "amongst the rarest and most desirable of coloured diamonds ever seen at auction".

Diamonds in the "fancy vivid" category are considered as having the highest possible concentration of colour.