Prince Harry has condemned the paparazzi for photographing his mother when she was critically injured in the wreckage of the car shortly after it crashed.

In an interview for a BBC documentary airing Sunday entitled Diana, 7 days, Harry speaks candidly about his mother's death. Princess Diana was in the back seat of a car that was travelling high speed through a tunnel in Paris while being pursued by the paparazzi.

Harry told the BBC that one of the most difficult things to accept is the paparazzi's behaviour in the immediate aftermath of the accident which caused her death.

"I think one of the hardest things to come to terms with is the fact that the people that chased her into the tunnel were the same people that were taking photographs of her while she was still dying on the back seat of the car," said Harry.

Harry said that he and his brother William had been told that numerous times by "people that know that was the case". "She'd had quite a severe head injury but she was very much still alive on the back seat," he added.

"And those people that caused the accident, instead of helping, were taking photographs of her dying on the back seat," said Harry.

Harry said "those photographs" subsequently made their way to news desks in the United Kingdom.

August 31 marks 20 years since Diana's death, and the princes are conducting a series of interviews to mark the event.

Diana, 7 Days, will be broadcast in the UK on BBC One on Sunday, 27 August at 7:30pm BST, and in the U.S. on NBC on September 1 from 8-10 p.m. ET/PT.