Koons has said his 14-metre (45-foot) -high inflatable "Seated Ballerina", installed this month above the statue of Hercules at Rockefeller Center, was inspired by a small Russian porcelain figurine from the end of the 19th century.

But many Ukrainians are crying foul, calling it a ripoff of "The Ballerina Lenochka", a porcelain statuette by Oksana Zhnikrup (1931-1993).

A spokeswoman for Koons, Lauran Rothstein, told AFP in an email that "We are aware of Oksana Zhnikrup's work and have a license to use it for Mr. Koons's work."

That apparently did little to calm Ukrainian tempers against the neo-pop artist.

"I hope that he has noted the source of his inspiration. If he forgot to do so, I advise the Ukrainian government to file a case," Ukrainian artist Oleksandr Roitburd said in a Facebook post.

"America will be surprised to see that we don't have just corruption and war, but also art," he said.

Koons has been accused of plagiarism before: In March he was ordered to pay a fine over his "Naked" sculpture, which was deemed a "counterfeit" of a French photograph.

Before that, he had been accused three times of copying works, and convicted twice.