Former Olympic swimming champion Grant Hackett is missing in Australia and needs urgent help, his father has said.

Hackett, 36, was on Wednesday arrested and released without charge after becoming agitated at his parents’ home.

His father, Nev, pleaded for public help on Thursday, saying he had not made contact for several hours.

Earlier in the day, Hackett posted a picture of himself on Instagram sporting a black eye. It was unclear when the image was taken.

“He’s definitely a missing person and he’s mentally disturbed and needs urgent help,” Nev Hackett told reporters.

Queensland Police officials confirmed they were “talking to a family in relation to a man”.

Family pleads for help

Hackett was last seen at a hotel on Queensland’s Gold Coast, according to local media.

Nev Hackett said his son had missed an appointment with his lawyer and the family was “extremely worried”.

“When we spoke to him several hours [ago], he just hung up when we asked him where he was,” he said.

“Grant, let us know where you are, we love you, and we want to help you,” he said.

Local media reported Hackett indicated he would seek help after being released from police custody on Wednesday.

His brother, Craig Hackett, said the former Olympian was “a danger to himself”.

Hackett, who won gold medals in the 1,500m freestyle and 4x200m freestyle relay at Sydney 2000 and in the 1,500m freestyle at Athens 2004, had a long-standing rivalry with compatriot Ian Thorpe.

He returned to the pool last year to make an unsuccessful bid to qualify for the Rio Olympics.

He was questioned by airport police in Melbourne last April after allegedly assaulting a male passenger over a reclined seat on a flight. Hackett said he had been drinking in the wake of his Olympic disappointment and publicly apologised.

Hackett has previously admitted he became dependent on a sleep medication.

The swimmer flew to the United States in 2014 to spend time in a rehab centre after he was spotted topless and disoriented in the lobby of a Melbourne casino.