An exhibition of banned erotic Japanese art has opened at London's British Museum.

Shunga: Sex and Pleasure in Japanese Art is a collection of 170 works from early modern Japan, a period when thousands of explicit works were created.

Shunga, or spring pictures, is a unique phenomenon in terms of the quality, quantity and nature of the art produced.

The exhibition looks at what sunga is, how it was circulated and why it was produced between 1600 and 1900.

Many of the works in the exhibition had been locked away for over 100 years because they were deemed so shocking and this is the first time many have been shown in public.

One of the more explicit images shows a woman being pleasured by an octopus. Another piece shows Samurai warriors visiting their male lovers, and two women having sex with a dildo.

The exhibition looks at the social and cultural context of sex in Japan. Shunga was mainly produced within the school of ukiyo-e, or pictures of the floating world. Many celebrated artists created shunga paintings - a complete contrast to Europe at the same time, where religion and moral beliefs enforced a division between art and porn.  

Shunga was banned after 1722 but it was rarely supressed in practice. Paintings were never censored and commercial lending libraries were not regulated.

Despite this, Japan was not a sexual free-for-all. Confucian laws and ethics focused on duty and restraint, while laws on adultery were severe. There were great divides in gender and class inequalities.

Tim Clark, curator of the exhibition, said: "We know it had a top, elite audience because the prints were extremely expensive, costing thousands of pounds. This was the top end of the market. There was also a mass audience for the illustrated books with dozens of illustrations in several volumes.

"The ambition of shunga is much, much wider. It talks about sexuality generally in society. It's meant to appeal as much to married couples, to courting couples, to people who want to use it for stimulation or seduction. It was certainly used as a sex manual."

Shunga: sex and pleasure in Japanese art will run at the British Museum until 5 January.The Trustees of the British Mu
Shunga was a popular art form in Japan between 1600 and 1900.Michael Fornitz collection
The exhibition looks at sexuality in society in Japan.The Trustees of the British Mu
Much of the art included in the exhibition was banned in Japan in the 20th century.The Trustees of the British Mu
The exhibition is the first time many of the art has been displayed in public.The Trustees of the British Mu
The British Museum advises parental guidance for visitors with children.The Trustees of the British Mu