British theoretical physicist Stephen Hawking says he rejects the idea of heaven or an afterlife, calling the belief a "fairy story" for people afraid of dying.

In an exclusive interview with The Guardian, Hawking, who has suffered from an incurable illness since the age of 21, says the prospects of dying as a young man led him to enjoy life more.

"I have lived with the prospect of an early death for the last 49 years. I'm not afraid of death, but I'm in no hurry to die. I have so much I want to do first," the 69-year-old scientist tells the British newspaper.

"I regard the brain as a computer which will stop working when its components fail. There is no heaven or afterlife for broken down computers; that is a fairy story for people afraid of the dark," he added.

The observations by Hawking, a theoretical physicist and cosmologist who won the Presidential Medal of Freedom, go beyond those discussed in his 2010 book, The Grand Design, in which he asserts that there is no need for a creator to explain the existence of the universe, the newspaper says.