The grey-bearded, black-haired entertainer said the milestone means he is about to either "turn truly wise" or become "old and cranky".

"So you'll have to ask my family which one applies to me," the star joked.

The big B, as he is known to his fans, will celebrate the event with the release of a book about his life called To Be or Not to Be.

Indian newspapers marked his birthday with interviews and special sections devoted to Bachchan.

The star, who became a grandfather in 1998, asked his fans to remain loyal after age steals his looks.

Everyone must accept "that we will age and age is not always flattering", he said.

Long career

The son of a Hindi poet, Bachchan quit his job as a freight broker in Calcutta and set off for Bombay in pursuit of a career in the movies.

Bachchan hosts India's Who Wants to be a Millionaire?

His acting career began in the 1970s and 1980s when he made his name as an action hero, a swashbuckling star of Hindi films.

He was also the narrator for the Oscar-nominated movie Lagaan.

Following a lean period in the 1990s, Bachchan came back bigger than before when he moved into making TV shows.

One of his most recent roles has been as host on the Indian version of quiz show Who Wants To Be A Millionaire?

Now, as the popularity of Indian movies and culture spreads increasingly into Europe, Bachchan is becoming a global star.

Fans voted him the millennium's biggest star in a BBC Online poll in 1999. Bachchan said the results "must be a computer error".