Sega released five free mobile versions of classic games for the iPhones and Android smartphones including Sonic the Hedgehog.

Available now via the Apple and Android app stores, the five first games will be followed by additional titles every two weeks though theSega Forever service.

The games include ads, but a single in-app purchase can disable them - this would cost $1.99.

Initially Sega is concentrating on games for the Master System, Mega Drive and Game Gear consoles but those made for the Dreamcast and Saturn would follow. The first five games on Sega Forever are:

• Sonic the Hedgehog
• Comix Zone
• Kid Chameleon
• Altered Beast

Games can be played via a portable device's touchscreen or by a controller. Sega said they would also be playable offline but people can save their progress online if they wish.