Banksy reveals how he shredded his own artwork 'Girl with a Balloon' at London auction

Secretive artist Banksy has revealed how he remotely destroyed his own artwork after it was sold at a London auction on Friday.

The auction of Banksy's 'Girl with a Balloon' was the climax of Sotheby's Friday evening (local time) sale, pulling in over NZ$2.1 million.

But just moments after it was sold, an alarm built into the painting went off and it self-destructed.

The frame, which was also made by Banksy, contained a shredder which began cutting the art into strips as patrons looked around in both awe and confusion.

On Instagram, the artist released footage showing him building the shredder into the frame.

"A few years ago I secretly built a shredder into a painting in case it was ever put up for auction," he wrote in the video.

Banksy captioned the video with the Picasso quote, "the urge to destroy is also a creative urge".

Some at the auction have speculated the elusive artist, who reportedly hates the art world, may have been in the room ready to push the button.

Sotheby's head of contemporary art for Europe, Alex Branczik, said he was not in on the ruse.