Music icon David Bowie only discovered his cancer was terminal three months before he died, according to a new documentary.

The superstar musician died on January 10, 2016, just days after turning 69 and ahead of the release of his 25th studio album - Blackstar.

A BBC documentary to be aired on what would have been Bowie's 70th birthday revealed that the singer found out his treatment was to be stopped as he was starring in death-shrouded music video "Lazarus", reports mirror.co.uk. 

Speaking on "David Bowie: The Last Five Years", director of the music video Johan Renck said: "I found out later that the week we were shooting is when he found out that it is over. We'll end treatment or whatever capacity that means, that his illness has won."

Renck added that the video, which features Bowie lying in a bed with his eyes covered by bandages and replaced with buttons, was not about the singer's illness.

"To me it had to do with the biblical aspect of it, you know the man who would rise again, and it had nothing to do with him being ill. That was only because I liked the imagery of it," he added.

"The Last Five Years" looks at the singer's acclaimed A Reality Tour in 2003 as well as the last four years of his life in which he returned with two albums after a 10-year absence and helped produce hit musical "Lazarus".

It includes rare and never-before-seen footage of Bowie and interviews during his Ziggy Stardust characterisation and is a follow-up to the acclaimed "David Bowie: Five Years", which was broadcast in 2013.