Myuran Sukumaran and Andrew Chan, members of the so-called "Bali Nine" sentenced on drug smuggling charges, were transferred Wednesday from prison to a maximum security facility where they will be isolated before being put to death.
Australia has repeatedly appealed for clemency for the pair. They have been jailed since April 2005 for a failed bid to smuggle more than 8 kilograms of heroin from Bali to Australia.
Australian Prime Minister Tony Abbott on Wednesday said "Australians are feeling sick in their guts at the prospect of execution for these two."
"We abhor drug crime, but we abhor the death penalty. We think that these two Australians deserve to be punished, but they certainly don't deserve to be executed," he said.
The Prime Minister said people should not let anger affect Australians' relationship with Indonesia.
The two men will be given 72 hours notice of their impending appointment with a 12-member firing squad once they arrive on the island of Nusakambangan. But precisely when is unclear. They are among a number of people from different countries who are also scheduled for execution.
The Bali Nine were arrested after Indonesian police received a tip from Australian Federal Police.
Chan, 31, was called the ringleader of the plot, and Sukumaran was described as Chan's collaborator in the scheme. Seven other people who participated in the plan are serving lengthy prison sentences.
Police caught four people at the Denpasar airport with more than 8 kilograms of heroin strapped to their bodies.
Another four -- including Sukumaran -- were arrested at a hotel in the village of Kuta. Chan was detained after a boarding a plane to Sydney -- he wasn't carrying any drugs but was named by others as the mastermind of the plot.
The Indonesian administrative court last week dismissed a case filed by lawyers of the two Australians against President Joko Widodo. The attorneys wanted a review of the president's decision to deny them clemency.
Todung Mulya Lubis, who represents the pair, said a challenge had been submitted to the administrative court and lawyers were still waiting for a court summons.
"There should be no execution as long as there is a legal process going on," Lubis said.
Sukumaran and Chan have become model prisoners during their time behind bars, according to fellow inmates and the jail's chief warden. Sukumaran is studying fine arts and has set up a class for fellow inmates. Chan has found spirituality, which he uses to counsel inmates with drug problems.
Their rehabilitation is genuine, Australian Foreign Minister Julie Bishop has said.
"Andrew and Myuran are the model of what penal systems the world over long to achieve," Bishop told the Australian Parliament in February.
Death for drugs
Indonesia has long taken a tough line on drug smugglers, and Widodo has made it clear he doesn't intend to introduce a policy of leniency.
In December, six prisoners were killed by firing squad
, including five foreigners from Brazil, the Netherlands, Malawi, Nigeria and Vietnam.
Brazilian President Dilma Rousseff issued a statement saying the execution of one of her countrymen had "severely affected" relations with Indonesia.