Two Australian drug smugglers in Indonesia were taken from their Bali prison to an island where they are to be executed, as the Australian leader said his country was "revolted" by their looming deaths after frantic diplomatic efforts to save them.

Andrew Chan, 31, and Myuran Sukumaran, 33, were taken to the airport in two armoured cars from the island's Kerobokan jail on Wednesday.

They are being transferred to Nusakambangan island, where several high-security prisons are located, the AFP news agency reported.

We abhor drug crime but we abhor the death penalty as well, which we think is beneath a country such as Indonesia. Tony Abbott, Australian PM

The men, members of the so-called "Bali Nine" were convicted of trying to smuggle heroin out of Indonesia in 2005 and sentenced to death the following year.

Local justice ministry official Nyoman Putra Surya said that the two men were woken up early and were given a few minutes to get ready.

The pair said "thank you" before leaving, and "we handcuffed them and they were quiet", he added.

Officials said they would be transferred on a chartered commercial flight, not on a military aircraft as had earlier been suggested.

Attorney-General Muhammad Prasetyo said on Tuesday that execution preparations were "95 percent" complete, and the last stage was gathering all the prisoners on Nusakambangan.

Australia 'revolted'

Speaking just before the transfer began, Australian Prime Minister Tony Abbott, who has repeatedly called for Jakarta not to go ahead with the executions, said millions of Australians were sickened by the developments.

"We abhor drug crime but we abhor the death penalty as well, which we think is beneath a country such as Indonesia," he told ABC radio.

"We frankly are revolted by the prospect of these executions."

Officials are yet to announce a date for their executions, but the transfer indicates it is imminent. Authorities must give convicts 72 hours notice before they are put to death.

They recently lost their appeals for presidential clemency, typically a death row convict's last chance to avoid the firing squad, and their looming executions have strained ties with Australia, traditionally a key ally of Indonesia.

The men are among a group of 10 drug convicts expected to face the firing squad in the upcoming batch of executions.

Officials have not confirmed the identities of the others, although convicts from France, Brazil, the Philippines, Nigeria and Ghana recently lost their appeals for presidential clemency.

Several countries have been piling diplomatic pressure on Jakarta, but President Joko Widodo has been a vocal supporter of the death penalty for drug traffickers, saying Indonesia is facing an "emergency" due to rising narcotics use.

Indonesia executed six people, including five foreigners, in January, sparking a diplomatic storm as Brazil and the Netherlands - whose citizens were among those executed - recalled their ambassadors.