Researchers hope that the machines could be used to treat patients within three years.

The news comes just weeks after a team of scientists announced that they had developed similar technology to carry out potentially life saving operations inside arteries.

The machines, part of a growing trend for so-called nano-technology, recall the plots of Hollywood science fiction movies, including 1987's Innerspace with Dennis Quaid, and the 1966 film Fantastic Voyage, starring Raquel Welch.

Sending drugs straight to cancer cells will mean that they do not damage other surrounding healthy tissue, researchers said.

The submarines are 100 times smaller than cells, according to Dr Dan Peer, head of nano medicine at Tel Aviv University in Israel, who has already tested them in mice.