A collection of works by celebrated graffiti artist Banksy have been sold in London.

Eighteen works went for a total of €486,211 − including the buyer’s premium − as part of Bonhams’ Urban Art sale.

The artwork included Girl and Balloon, a 2009 work which fetched €87,846, almost five times more than its pre-sale estimate of €29,981.

The image has been painted directly onto the cardboard backing of an Ikea frame and is signed and inscribed: “For Mike. Thanks”.

Another highlight was a stencil painting, Leopard and Barcode. Bought from Banksy’s Existencilism exhibition in Los Angeles, the painting has never been offered at auction before.

It attracted a pre-sale estimate of €95,941 and was sold for €90,724. In a separate auction at Bonhams, a screenprint of a dollar sign by American pop artist Andy Warhol was sold for €53,307.

Initially painted onto a handkerchief and given to friends in 1981, the picture has been mounted onto board.

Measuring 35.5cm by 25cm, it attracted a pre-sale estimate of €35,977. A spokesman for Bonhams said that the auction house could not disclose the identity of the seller or buyer of the screenprint.

Other contemporary artwork sold at the auction included an oil and watercolour painting by German visual artist Gerhard Richter which fetched €159,800 − nearly 10 times more than its pre-sale estimate.