Harry’s highly personal book “Spare” went on sale in Spain days before its global launch on Jan 10.

It discloses the depth of the rift between the prince and his brother William, the heir to the throne, and other revelations such as drug-taking and how he lost his virginity.

In one section, the 38-year-old recounts his two tours of Afghanistan, first as a forward air controller in 2007-08 and again in 2012, when he was a co-pilot gunner in Apache attack helicopters, and the number of people he had killed.

“It wasn’t a statistic that filled me with pride but nor did it leave me ashamed,” Harry wrote, according to the Spanish version of the book. “When I found myself plunged in the heat and confusion of combat I didn’t think of those 25 as people.

“They were chess pieces removed from the board, Bad people eliminated before they could kill Good people.”

Anas Haqqani, a senior Taliban leader, criticised the Duke of Sussex over the remarks, saying those Harry killed were Afghans who had families.

“Mr Harry! The ones you killed were not chess pieces, they were humans,” Haqqani tweeted, accusing the prince of committing “war crimes”.

“The truth is what you’ve said; Our innocent people were chess pieces to your soldiers, military and political leaders.

“Still, you were defeated in that ‘game’.”

Abdul Qahar Balkhi, spokesperson for the Taliban-led Afghan foreign affairs ministry, also criticised Harry’s comments.

“The western occupation of Afghanistan is truly an odious moment in human history and comments by Prince Harry is a microcosm of the trauma experienced by Afghans at the hands of occupation forces who murdered innocents without any accountability,” he said.

Harry served 10 years in the British military, rising to the rank of captain.

He carried out two tours of duty against the Taliban, first as a forward air controller calling in air strikes in 2007 and 2008, and later flying an attack helicopter in 2012 and 2013.

Cameras mounted on the nose of his Apache helicopter enabled him to assess his missions and determine with certainty how many he had killed.

He justified his actions using the memory of the 9/11 attacks in the United States and after meeting families of the victims.

Those responsible and their sympathisers were “enemies of humanity” and fighting them was an act of vengeance for a crime against humanity, he wrote in the book.

Harry has since voiced concern about his security due to his royal status and time fighting militants.