SYDNEY (AFP) - Australian Prime Minister Tony Abbott said he had done all he could to save the lives of two of his citizens facing imminent execution in Indonesia on Thursday, as their lawyers admitted the situation was "bleak".

Andrew Chan and Myuran Sukumaran, ringleaders of the so-called "Bali Nine" drug smuggling gang, lost a legal bid in the Balinese capital Denpasar to have their cases reviewed on Wednesday, dashing their final hope of avoiding the firing squad.

Mr Abbott said on Thursday his government had "left no stone unturned" in the bid to save them. "We oppose the death penalty, we do whatever we humanly can to try to ensure that no Australian suffers the death penalty," he told reporters. "We are not going to engage in last-minute, megaphone diplomacy but I just want to assure people that the Australian government has left no stone unturned to try to ensure that these two Australians on death row have their sentences commuted."

Chan and Sukumaran's lawyers based their argument for a reprieve on past legal errors, and said the pair had been rehabilitated and this should be considered. The pair's Australian lawyer Julian McMahon said he would work to continue their legal fight despite the setback. "The basis of the application actually was that there was error of law so what we're looking at now are the legal options that flow from that but there's no doubt the situation is bleak," he told ABC radio.

The duo were arrested in 2005 and sentenced to death the following year for attempting to smuggle heroin out of Indonesia.

Despite his image as a reformist, Indonesia's President Joko Widodo has been a vocal supporter of capital punishment for drug offenders, disappointing rights activists who had hoped that he would take a softer line on the death penalty.

Last month Indonesia executed six drug offenders, including five foreigners, prompting a furious Brazil and the Netherlands - whose citizens were among those put to death - to recall their ambassadors.

Mr McMahon said Chan and Sukumaran had been "just caught up in a giant political move here, and the merits of my clients' cases don't seem to be being given the attention that they deserve".

Mr Abbott has appealed for Jakarta not to go ahead with the executions but Mr Joko, known as Jokowi, reiterated his tough line on Wednesday that traffickers would not be granted clemency.

No date has been set for their executions, although Australian media reports suggest they could be put to death within a fortnight.