Australian teenager Jamie Murphy's Bali nightmare over

Australian Jamie Murphy, center, is escorted by plain-clothed police officers upon his release from police custody in Bali, indonesia. Photo / AP

Australian teenager Jamie Murphy's nightmare in Bali, where he was locked up for two nights and faced years of jail time, is over after he landed home in Perth.

Airport staff whisked the 18-year-old and his parents Brendan and Anna Murphy through a private exit to a waiting van to avoid the media.

Murphy was arrested early on Tuesday outside the Kuta nightclub Sky Garden for carrying a bag of white powder.

Film emerged of him being physically roughed up by a security guard who appeared to be choking him and squashing his face, as a distressed Murphy pleaded "it's not mine ... what are you doing?"

Murphy finished school last year but arrived in Bali on Sunday night with two friends celebrating graduation.

Police said they suspected the 1.6g of white powder he was caught with was heroin or cocaine - an offence that carries with it a maximum of 12 years in prison.

Kuta police chief Wayan Sumara said the powder turned out to be a mixture of painkillers, caffeine, cold and flu medication and cough medication.

Describing Murphy as "very lucky", he said the teen had bought it off a man on the street who told him it would "make him feel good".

"I don't want to say whether he is stupid or not."

Sky Garden apologised for the "excessive force" used during his detainment.

They said the security guard involved in the teenager's detainment has been "reprimanded" and will undergo further training.

- AAP