Banksy street art up for auction

One, Donkey Documents, depicts a donkey having its papers checked by a soldier and was left on a barrier dividing the West Bank from Israel in 2007.

The other, I Remember When All This Was Trees, was painted on the wall of a derelict Detroit factory in 2010.

Together the murals could fetch as much as $1 million (£638,000).

The Detroit mural is owned by a small non-profit gallery and is being sold to raise funds for community arts schemes.

Auction house Julien's has not revealed who removed the second work from its original location or who will benefit from its sale.

According to Julien's, "the detached mural... is the largest and most significant intact Banksy mural in existence from his visit to Israel".

The mural, it continued, will be displayed at an unspecified location in London before the auction takes place in Los Angeles on 30 September.

Removing street art by Banksy and others from their original locations is a controversial act that some claim diminishes the artwork in question.

The removal of one mural from a shop in north London prompted protests, though this did not prevent its eventual sale for more than £750,000.