Swimmers Josh Palmer and gold medallist Emma McKeon were grounded after Palmer was left disorientated in Copacabana, and McKeon stayed with a friend overnight without notifying team management.

The pair had been with a group of Australian swimmers at a Copacabana nightclub but chose not to accompany their teammates back to the athletes' village. It is understood they were still in the nightclub at 4am on Wednesday morning.

A statement issued on Thursday morning, Rio time, by the AOC boss Kitty Chiller said McKeon, 22, and Palmer, 25, must now remain in the village between 8pm and 8am and only travel to sporting events in official Rio 2016 transport.

They have been banned from participating in the closing ceremony. McKeon had been a strong contender for the honour of carrying the Aussie flag at the event.

"Palmer and McKeon's behaviour was unacceptable and they breached disciplinary protocols. I have raised the need for the swimming team leader to ensure he is aware of his athlete's whereabouts when leaving the Olympic Village and that the swimming athletes observe the 2am curfew", the statement said.

Palmer told officials he was approached by a man who forced him to withdraw the money from a nearby ATM.

Chiller said Palmer was found later by two businessmen in Copacabana who reported the swimmer was disoriented and had lost his wallet and phone. They phoned the Australian Consulate who then contacted the team's head of security.

On Thursday afternoon, McKeon tweeted her disappointment.

Rio is notorious for such crime and athletes from several countries have been told to be extremely vigilant when out.

Overnight, a British athlete was robbed at gunpoint and US gold medal swimmers were barred from leaving Brazil by a judge who wants to ask more questions regarding their seemingly contradictory accounts of an incident involving a taxi, a gun and a boozy night out. The highest profile of the four American swimmers Ryan Lochte, had already arrived back on home soil when the order was made.

Last week, Chiller told athletes to stay off the sand on Rio beaches at night.

She earlier had also "read the riot act" to Australia's men's sevens players after a drunken night out in Copacabana.

Twenty-two year old McKeon won one gold medal, two silver and one bronze at the Rio Games. According to Chiller, she chose to stay in Copacabana with a friend after their night out without informing team management.

Palmer, who finished fifth in heat three of the 100m breaststroke the first day of competition, then headed off to a beach kiosk to continue drinking with a friend, before being robbed.

He chose not to lodge a police complaint.