Singapore swimmer Joseph Schooling apologizes for cannabis use at Hanoi SEA Games

Singapore has some of the toughest drug laws in the world, and its citizens and permanent residents face up to 10 years in prison if found to have consumed illegal substances outside the city-state.

Schooling, who has been performing his two years of mandatory military service, tested negative for drugs but confessed to consuming cannabis overseas in May, the defense ministry said in a statement late Tuesday.

At the time of the offense, Schooling had been allowed to pause his national service to train and participate in the Southeast Asian Games in Hanoi, where he won two golds and a bronze.

"Given his abuse of disruption privileges, (Private) Schooling will no longer be eligible for leave or disruption to train or compete while in NS (National Service)," the ministry said.

The 27-year-old was given a warning and will be placed on a supervised urine test regime for six months, the ministry added.

Singapore requires all male citizens aged more than 18 to serve two years in the military, the police or the emergency services, an obligation authorities rarely let people skip.

The Rio 2016 gold medalist in 100m butterfly -- Singapore's only Olympic gold in its history -- apologized in a statement but gave no details about his plans for his swimming career.

"I gave in to a moment of weakness after going through a very tough period of my life," he said.

"I made a mistake and I'm responsible for what I've done... I won't let you down again."

Schooling caused a sensation at Rio 2016 when he beat Michael Phelps to win the 100m butterfly.

But the city-state's first-ever Olympic champion relinquished his title after failing to qualify in the same event at last year's Tokyo Games, and has dropped several hints recently that his career is coming to an end.