Two convicted Australian drug smugglers were transferred on Wednesday from a Bali prison to an island for execution along with other foreigners, underlining Indonesia's determination to use the death penalty despite international criticism.

The planned executions of Myuran Sukumaran, 33, and Andrew Chan, 31, have ratcheted up diplomatic tensions between Australia and Indonesia following repeated pleas for mercy on their behalf. They are among 11 death row convicts scheduled to go before a firing squad on the prison island of Nusakambangan.

Sukumaran and Chan left Bali's Kerobokan Prison in an armoured van with a police escort before dawn and were taken to Denpasar airport for a flight to the Javanese port of Cilacap for the trip to Nusakambangan.

Armoured vans boarded a boat in Cilacap and the Australians arrived at Nusakambangan soon after, a Reuters photographer reported.

A Frenchman and a Brazilian are already on the island. Also facing execution are citizens of the Philippines, Ghana and Nigeria, as well as Indonesia.

Indonesia's attorney general's office confirmed the transfer but is yet to give the usual public 72-hour notice of any execution.

Australian Prime Minister Tony Abbott said he was "revolted by the prospect of these executions", after Indonesian President Joko Widodo recently told other countries to stay out of his country's sovereign affairs.

Widodo has adopted a tough stance against drug traffickers and others on death row, denying clemency to the 11 convicts. Executions were resumed in 2013 after a five-year gap and nationals from Brazil, Malawi, the Netherlands, Nigeria and Vietnam have been among those put in front of a firing squad.

"I think there are millions of Australians who feel sick to their stomachs about what's likely to happen to these two men who committed a terrible crime, a terrible crime," Abbott told Australian Broadcasting Corp. radio.

"The position of Australia is that we abhor drug crime but we abhor the death penalty as well, which we think is beneath a country like Indonesia."

Chan and Sukumaran were convicted in 2005 as the ringleaders of the so-called Bali Nine, who were arrested at Denpasar airport for trying to smuggle 8 kg (18 lb) of heroin to Australia.

The Australian government has stressed they have been rehabilitated in prison, where they mentored younger inmates, and has warned of potential political repercussions if the executions go ahead.

A survey by the Sydney-based Lowy Institute think tank showed strong public disapproval of the executions, with 62 percent of the 1,211 people surveyed opposing the move. A social media campaign is urging Australians to boycott Bali, a popular destination.

However, one business executive in Australia criticized the government's support for the pair, saying it had soured ties with Indonesia.

"Some of the public statements made by our most senior politicians demonstrate that they have a very naive understanding of the importance of Indonesia to Australia," Peter Lynch, chairman and CEO of coal miner Cokal Ltd, told Reuters.

Cokal, which is developing a coal project in Kalimantan on Indonesia's side of Borneo island, on Tuesday received a takeover offer worth at least $54 million from Indonesian firm Cakra Mineral Tbk.

Putra Surya Atmaja, head of the provincial prison division in Bali, told reporters Sukumaran and Chan were being transferred after having "plenty of chances and time with the family".

The pair have made numerous appeals against their death penalty sentence. One of those, which challenges Widodo's refusal of clemency, is still outstanding.

Peter Morrissey, a Melbourne-based lawyer for the men, said it would be a breach of the rule of law if the executions went ahead before that was resolved.

Asked before the early-morning transfer if the pair were prepared for execution, Morrissey said: "They're coming to terms with that ... it's a very raw time for them."

Abbott said Australia's lobbying on their behalf had shown some promise, but he no longer wanted to hold out false hope.

"There were some suggestions earlier that perhaps at least some people in the Indonesian systems were having second thoughts but I'm afraid those signals seem to be dissipating," he said