Japan on Wednesday finally fell into line with other major developed countries and made the possession of child pornography illegal, but the sometimes graphic images of pedophilia in manga comic books remain legal.

The upper house of parliament voted overwhelmingly for a bill revising laws under which only the production and distribution of child pornography had been banned. The legislation cleared the lower house earlier this month.

Campaigners had long urged Japan to toughen its stance on child pornography, complaining it was a major source of the material for global markets. The new legislation bans possession of photographs and videos depicting real children aged below 18, but it does not include drawings or digitally-created imagery.

Now anyone who "possesses child pornography for the purpose of satisfying his/her sexual interest" faces imprisonment of up to one year or a fine of up to 1 million yen ($9,800).

To encourage disposal of material, the penalties will be delayed for one year after the revised law comes into effect, which could happen in July.

The ban excludes "manga" comics - those aimed at adults as well as children, "anime" video and computer-generated graphics, following calls to protect freedom of expression.

Japan was the only member of the G7 in which the possession of child porn remained legal. It is banned in more than 70 countries.