Andrew Chan and Myuran Sukumaran have joined about 2000 other prisoners on Nusakambangan island.
Known as the Alcatraz of Indonesia, Nusakambangan island in Central Java contains maximum-security prisons holding convicted terrorists, murderers, drug dealers and political dissidents.
About 2000 criminals - many wearing prison garbs in shades of blue - are believed to be held in the network of seven high-walled prisons, first built by Dutch colonists in 1908.
Wednesday's development came amid signs of a breakdown in communication between the Indonesian and Australian governments, with Foreign Affairs Minister Julie Bishop admitting there had been no official confirmation from Indonesian officials that a transfer was going to take place.
The extraordinary security measures reflect concerns about an unspecified threat but also show how the execution of the pair has been swept up by nationalist fervour and turned into a spectacle.
The Australians were accompanied by a large contingent of members of the elite paramilitary police, known as Brimob, on the Wings Air jet.
They were also accompanied by the man formally in charge of the transfer, Bali's chief prosecutor Momock Bambang Samiarso.
Chan and Sukumaran flew to Cilacap, the port town near the prison island of Nusakambangan, a journey that took about one hour.
Security was extraordinary for Chan and Sukumaran's journey to Nusakambangan: fighter jets shadowing their plane, armoured vehicles, helicopters and hundreds of troops on standby in Cilacap airport for their arrival.
Where are Chan and Sukumaran being taken?
Known as the Alcatraz of Indonesia, Nusakambangan island in Central Java contains maximum-security prisons holding convicted terrorists, murderers, drug dealers and political dissidents.
About 2000 criminals - many wearing prison garbs in shades of blue - are believed to be held in the network of seven high-walled prisons, first built by Dutch colonists in 1908.
When will the execution date be announced?
The prisoners will be given 72 hours' notice of their execution time. Indonesia's attorney-general HM Prasetyo said it would take place "ASAP".
The killing of a previous group of prisoners was delayed by weather problems, journalists masquerading as fishermen to try and access the island and confusion over the religion of those condemned.
What does the execution involve?
Death row inmates are blindfolded, asked to stand, sit or kneel, and simultaneously fired upon by 12 executioners aiming for their chests. Chan and Sukumaran are set to be killed alongside another eight drug felons, which means a total firing squad of 120, drawn from Indonesia's paramilitary forces.
If the prisoner is still breathing, the commander will shoot him or her point-blank in the head.
Channel Nine has released pictures of what it claims to be the wall victims will be lined up against.
Can the prisoners see their families while on the island?
Chan and Sukumaran will be allowed to meet their families and lawyers and receive comfort from religious figures.
Chan's brother Michael and Sukumaran's mother Raji visited the pair on Tuesday but left the penitentiary before news emerged of the timing of their transfer. Other family members are expected to come over from Australia soon.
On Wednesday morning, Andrew Chan's brother Michael was frantically arranging a flight to Cilacap, the port town near Nusakambangan.
Are there any legal options left?
Todung Mulya Lubis, the lawyer representing Chan and Sukumaran, has pleaded with Indonesian authorities to "please wait" before executing the pair until all of their legal avenues have been exhausted.
In a statement on Tuesday, lawyers said the men had challenged the dismissal to their appeal in the Jakarta State Administrative Court on Monday.
Secondly, they had submitted a report to the Judicial Commission on February 13 alleging violations of judicial conduct and ethics.
Indonesia's attorney-general Prasetyo said on Monday that legal appeals pending for Chan and Sukumaran would not have any impact on the executions.
What is the government doing?
Communication between Indonesia and Australia over details of the men's execution seems to have broken down, with no official confirmation of the transfer.
Foreign Minister Julie Bishop said she was "utterly dismayed" to learn the Australians were being moved without all of their legal avenues having been exhausted. Prime Minister Tony Abbott said he still held out hope for a reprieve, and continued to make representations to the Indonesian government.
Who are the other prisoners set to be killed alongside the Bali nine members?
They are Mary Jane Fiesta Veloso (Philippines), Serge Areski Atlaoui (France), Martin Anderson alias Belo (Ghana), Raheem Agbaje Salami (Nigeria), Rodrigo Gularte (Brazil), Zainal Abidin (Indonesia), Silvester Obiekwe (Nigeria) and Okwudili Ayotanze (Nigeria). Read more about their stories here.
Heavy military guard
Chan and Sukumaran were taken from Kerobokan prison under heavy military guard in the early hours of Wednesday.
They were driven through the gates of Kerobokan in a Wolf armoured personnel carrier. They were followed by police in a Barracuda armoured vehicle.
Streets were blocked off and two buses of crowd-control police carrying riot shields and batons were deployed along with a contingent of military. A water cannon was stationed outside the prison in case of trouble.
The Australians were taken to Denpasar airport.
