The son of Dubai’s ruler has died of a heart attack at the age of 33, the United Arab Emirates state news agency WAM said.

“Today, I lost a best friend and a childhood companion, my dear brother Rashid,” said Sheikh Hamdan bin Mohammed, Crown Prince of Dubai. “You will be missed.”

President Sheikh Khalifa declared three days of mourning across the UAE, with flags at government departments and institutions to fly at half mast. Sheikh Khalifa expressed his heartfelt condolences and solace to Sheikh Mohammed.

Prayers will be held at Zabeel mosque on Saturday evening and he will then be buried in Umm Harir cemetery in Bur Dubai.

Sheikh Rashid was the first son of Sheikh Mohammed from his senior wife, Sheikha Hind.

His younger brother Sheikh Hamdan is Dubai’s crown prince.

The young prince attended Sandhurst Military Academy in the United Kingdom and graduated in 2002.

He was also an avid sportsman and horse racing enthusiast, and owned Zabeel Stables. He participated in international equestrian events and had won a number of medals.

Rashid headed the UAE Olympic Committee briefly in 2008, before resigning two years later citing work overload.

His personal net worth was estimated by Forbes in 2010 to be $1.9bn.

Agencies/Canadajournal