A Gustav Klimt portrait painting has sold for $A363 million, a record for a modern art piece, at an auction where a solid gold, fully functional toilet satirising the ultra rich also fetched $A18.6 million.

The toilet, by Maurizio Cattelan - the provocative Italian artist known for taping a banana to a wall - went up for auction Tuesday evening at Sotheby's in New York.

The starting bid for the 101kg, 18-karat-gold work was about $US10 million ($A15 million).

Cattelan has said the piece, titled 'America', satirises super wealth.

"Whatever you eat, a $200 lunch or a $2 hot dog, the results are the same, toilet-wise," he once said. Sotheby's, for its part, calls the commode an "incisive commentary on the collision of artistic production and commodity value".

Klimt's 'Portrait of Elisabe

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