A rare print of street artist Banksy's famous Girl With Balloon artwork is expected to sell for up to £350,000 ($450,000), Sky news reports.

While it usually features a red balloon, this one is purple - and one of just 88 created with different colours.

It is up for grabs at Christie's as part of the auction house's second sale dedicated to Banksy.

The online auction is already under way and has a starting bid of £240,000 ($308,000), with a final estimate of £250,000 to £350,000 (320,000-450,000).

The sale of the 69cm x 49cm artwork finishes on September 23.

The sale is titled Banksy: I Can't Believe You Morons Actually Buy This S***, after the anonymous street artist's Morons artwork, and includes 22 lots.