The red-eye flight had left Melbourne Airport for Kuala Lumpur when trouble began.
"One air hostess just screamed 'Help, help help', so we tried … but (we were a) couple of seats away," passenger Arif Chaudhery from Pakistan told Channel NewsAsia.
"We tried to (tackle) him on the floor, face down."
The passengers helped the flight crew restrain the passenger, a Sri Lankan national who was apparently drunk.
Malaysia's Deputy Transport Minister Abdul Aziz Kaprawi later confirmed that the passenger was carrying a powerbank, and not a bomb as some reports had initially claimed.
Mr Chaudhery said that they spent about an hour and a half in the plane, before they were evacuated by police and security staff.
"The police were carrying guns. One by one, we were evacuated. The 'special police' were on board the plane," he said.
The passengers were on the tarmac, waiting to go back into the terminal at Melbourne Airport, he told Channel NewsAsia on the phone.
"At the moment, we are sitting here, we don’t know much information. The airport staff just called us, we haven’t been informed at the moment.
"Where they are going to take us - back on the plane? At the moment, (we are) just sitting. We don’t know at this stage."
A spokesman for Melbourne Airport said that all flights at the airport were affected by the incident, and a Malaysia Airlines spokesperson said that MH128 passengers would be put up at hotels and offered the next available flight on the airline or on other carriers.
Mr Chaudhery had reason to be anxious to be on his way.
"My mum is passing on in the ICU in my country," he told Channel NewsAsia. "It could be worse. I might still be lucky."
- Channel News Asia