Japanese artist's decade old mural could be worth millions

A decade old mural on the inside of a New York bar could soon be worth $7 million.

The value of Japanese artist Yoshitomo Nara's work at Niagara bar in the East Village is predicted to skyrocket after his "Knife Behind Back" painting sold for $37 million (US$25 million) at Sotheby's Hong Kong. The sale was a record for the artist.

"(The mural's) been just hanging out for 10 years," the artist's long-time representative Tim Blum told the New York Post.

"Nobody paid it too much attention until now."

Independent curator and adviser Sharon Hurowitz said "the sky was the limit" when it came to a final price for Nara's street art.

"It's something people would grab onto and be interested in," she told the Post. "You could see another sensational price."

Nara first pulled out a marker and started drawing his signature doe-eyed cartoon-like characters unintentionally on the wall after a couple of drinks back in late February 2009.

"He felt particularly free that night," Mr Blum told the media outlet.

"One thing led to another, and it was quite unscripted. Nobody got in the way."