BELFAST (AFP) – A friend of Prince Charles who had been head of an exclusive polo club was killed when a helicopter crashed in Northern Ireland, a spokeswoman for the royal family said.

Charles Stisted, who was chief executive of the Guards Polo Club, was one of three men killed in the accident Saturday in Northern Ireland's Mourne Mountains.

The club was reportedly a favourite with the royals, and Stisted, 47, was also known to Prince William and Prince Harry and Charles's wife Camilla.

Charles, the 61-year-old heir to the British throne, used to play at the club until his retirement from the sport in 2005 and his sons William and Harry are current members, reported Britain's Telegraph newspaper.

Charles, his sons and Camilla were "shocked and deeply saddened" by the tragedy, said a spokeswoman for the royals Sunday.

"The Prince of Wales [Charles], The Duchess of Cornwall [Camilla], Prince William and Prince Harry are all shocked and deeply saddened by this terrible tragedy," said the spokeswoman.

"Their Royal Highnesses' thoughts and prayers are with the families of those killed at this dreadful time."

The polo club is in Windsor, which is the location of one of Queen Elizabeth II's official residences, Windsor Castle.

The group was thought to be on its way back from a hunting trip when the accident happened. Emergency services were scrambled to the mountains in County Down after a witness reported seeing the helicopter in distress.

But police confirmed later neither the pilot nor his two passengers survived the impact.

The Mournes are internationally renowned for their picturesque scenery. The coastal mountain range is designated as an area of outstanding natural beauty.