A promising Australian jockey has died in Singapore after falling from his high-rise apartment block in an apparent accident, the city-state's horse racing body said Wednesday.

Tim Bell, 22, died late Tuesday, Singapore Turf Club said, adding that unconfirmed reports claimed he was trying to scale the building after being locked out.

Singapore police said they were investigating the "unnatural death". In such cases, a state coroner is appointed to establish the cause of death.

A statement on the turf club's website said details about the incident remain sketchy.

"But from unconfirmed reports it appears that Bell, 22, locked himself out from his unit, and fell to his death after attempting to climb up to the 12th storey apartment to get his house keys," it said.

"The Singapore Turf Club would like to express its heartfelt condolences to Tim's family and friends."

The Singapore Police Force said they received a call for assistance at 7:12pm (1112 GMT) on Tuesday.

"Upon police's arrival, a 22-year-old man was found lying motionless at the foot of the said building. He was conveyed unconscious to Khoo Teck Puat Hospital where he later succumbed to his injuries," it added in a statement.

Trainer Steven Burridge, who was instrumental in bringing Bell to Singapore on a three-and-a-half-month contract, described the accident as a tragedy.

"Timmy had the whole future ahead of him and not only could he ride, but he was also such a great young man, and was very driven to become a very good jockey," Burridge said on the turf club website.

Bell had already bagged five wins in Singapore, the club said.

Australian media described Bell as a rising star in the sport, winning the 2013-2014 Brisbane jockey's premiership in his first season as a senior jockey.

In Australia, the Narrabri-born Bell rode 650 winners in a career spanning seven years, including more than 20 at group level.