A Malaysia Airlines plane had to return to the airport after a passenger tried to enter the cockpit.
The plane has returned to the ground safely, requesting security assistance.
MH128 landed safely at Melbourne Airport at 11.41pm (1.41am Thursday NZT), the company said.
All other passengers have since disembarked without any reported casualties.
Malaysia Airlines released a statement that said the flight was diverted due to a "disruptive passenger" but denied it was an attempted "hijacking".
The passenger, a Sri Lankan national who was apparently drunk, was overpowered by the plane's crew and later arrested at Melbourne's airport, he said.
Passengers worked with the flight crew to subdue the man.
"Following the incident on MH128, the disruptive passenger has been apprehended by airport security".
The crew returned to Melbourne and performed an overweight landing about 15 minutes after departure and was located to a remote part of the airport.
Saiqa Chaudhery, who said her husband Arif was on the plane, alleged the passenger was under the influence of drugs or alcohol and that he attacked a flight attendant.
The Star reports Malaysia's Deputy Transport Minister Datuk Seri Aziz Ab Kaprawi said the device the man was holding was not a bomb.
Victoria Police later said the incident was not being treated as terrorism and that the man's object was not a bomb.
The plane turned back to Melbourne airport when the incident began.
The Malaysian Airlines statement claimed the plane was in the air for just over 30 minutes of an eight-hour flight time, however flight tracking website FlightRadar24 said it was only in the air for 14 minutes. Later that same year, Flight MH17 from Amsterdam to Kuala Lumpur was shot down in eastern Ukraine.
Dramatic pictures captured on board flight MH128 show how the man was tied down when he was restrained shortly after the plane took off from Melbourne to Kuala Lumpur.
Passengers have been safetly removed from the plane are being accommodated at hotels or offered additional flights. "At the moment, the airline does not wish to make any premature conclusions until a full investigation has been concluded".