Former Beatle John Lennon is featuring in a charity's TV advertisement in the US, to help bring solar-powered computers to the world's poorest children.

The singer, who was killed 28 years ago, has been brought back to life using digital technology for the One Laptop Per Child initiative.

His widow, Yoko Ono, gave permission for his image to be used in the commercial, in which he is seen saying: "Imagine every child, no matter where in the world they were, could access a universe of knowledge.

"They would have a chance to learn, to dream, to achieve anything they want. I tried to do it through my music, but now you can do it in a very different way."

Lennon was shot and killed in December 1980 as he and wife Yoko Ono arrived at their apartment building next to Central Park, New York. The commercial will air on spots donated by broadcasters, and has also been placed on YouTube. . The One Laptop Per Child Foundation, created in 2005, started producing XO laptops late last year at a cost per machine of less than $200 (s135).

In the commercial, multi-colored pixels bombard the screen until they form an image of Lennon, who speaks into the camera to relay the charity's message.