The Papua New Guinea army has been sent to Manus Island to clear out hundreds of men still refusing to leave the detention centre.
"Move, move, you have one hour to move," asylum seekers say the authorities screamed at them as they entered.
It comes as footage emerges of PNG authorities storming the mothballed Manus Island detention centre, demanding the hundreds of men inside leave immediately.
Immigration Minister Peter Dutton has confirmed a police operation at the detention centre, and said the men who remain — about 400 of them — will be moved.
Several asylum seekers have taken to Twitter describing high tension in the centre, writing that PNG authorities were aggressively telling them to leave.
"The police, special forces, police squad are now in their hundreds, spreading through the prison camp and around the prison," Iraninan Behrouz Boochani tweeted.
"Navy soldiers are outside the prison camp. We are on high alert right now. We are under attack," he said.
"Immigration and police started searching the rooms and are saying 'Move Move' you only have an hour to move".
"Too much stress and tension here in Delta. Some refugees are crying."
"They are taking the phones and are very aggressive and are taking out some refugees who still remain in the rooms. Something terrible is happening right now, they are taking the refugees out of the rooms.
"They are destroying everything. Shelters, tanks, beds and all of our belongings. They are very aggressive and put our belongings in the rubbish bins. The refugees still are silent are watching them so scared."
At one stage, he said, he was tweeting from a toilet block as "they detroyed everything"
Fellow detainee Ezatullah Kakar tweeted the asylum seekers were peaceful, but scared, and "everyone is crying".
Dutton told the Australian radio station 2GB: "We're very keen for people to move out of the Manus regional processing centre. I think it's outrageous that people are still there and they have trashed the facility, they are living in squalor, and the Australian taxpayers have paid about $10 million for a new facility and we want people to move."
"And obviously, it's in the end an issue for PNG police and the authorities up there but is an operation involving police in the centre this morning."
The intervention comes after twelve former Australians of the Year penned an open letter asking Prime Minister Malcolm Turnbull and Opposition Leader Bill Shorten to immediately allow doctors access to asylum seekers in the facility.
The group warns Australia's reputation on human rights is deteriorating because of the failure to meet the obligations of the UN Refugee Convention.
"We believe it is time to stop the unacceptable and internationally criticised treatment of the refugees on Manus Island, who, though innocent of any crime, have been incarcerated and now abandoned there," the letter says.