The two Australian Bali Nine drug smugglers on death row, Andrew Chan and Myuran Sukumaran, have received formal notification they will be executed soon.

Sukumaran let it be known on Saturday that he believed he had only days to live before he was executed.

The pair received a briefing from their lawyers on the intentions of Indonesian authorities during a visit to the prison island of Nusakambangan.

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One of the self-portraits painted by Sukumaran.

The lawyers returned to the mainland with three colour self-portraits painted by Sukumaran.

The 34-year-old had inscribed on one of the artworks: “Self portrait – 72 hours just started.”

It was dated 25 April, 2015, “Besi Prison, Nusakambangan”.

Sukumaran’s reference to the 72 hours relates to a process Indonesia has laid out for itself after an international backlash to its resumption of executions in January.

The procedure outlined by Indonesia’s attorney-general Muhammad Prasetyo and repeated by spokesman Tony Spontana is to give a minimum of 72 hours’ notice before the next 10 criminals face the firing squads.

Those facing execution alongside Chan and Sukumaran include convicts from Brazil, Nigeria and the Philippines.

One prisoner, a French national, has been granted a temporary reprieve after Paris stepped up pressure on Jakarta.

Lawyer Julian McMahon emerged from meetings with his client Myuran Sukumaran carrying three self-portraits.

Earlier on Saturday, Indonesian government officials called consular teams for the foreigners due to be executed to explain rules and processes, including how death row prisoners’ “last requests” would be met.

Australia’s Foreign Minister Julie Bishop concluded that the executions of Chan and Sukumaran would be “scheduled imminently”.

Ms Bishop added that she had spoken to Sukumaran’s mother, Raji, “and assured her the Government would continue to seek clemency from Indonesian president [Joko] Widodo for both men”.

All indications are that Indonesia will not waver in its determination to carry out the death sentences.

However, United Nations chief Ban Ki-moon appealed to Indonesia to spare the group from execution.

“The Secretary General appeals to the government of Indonesia to refrain from carrying out the execution, as announced, of 10 prisoners on death row for alleged drug-related crimes,” a spokesman for Mr Ban said.

Relatives of Chan and Sukumaran are planning to make a visit to Nusakambangan on Sunday — which hints at further confirmation that the pair have entered the final 72-hour notification period.

Sunday is not a regular prison visit day at Nusakambangan. Rules governing family visits are more liberal within the final days.

On Monday, a legal challenge by the Indonesian death row prisoner Zainal Abidin is set to be confirmed as lost, giving the Indonesian government more reason to step up preparations for the group of ten.

But predicting the timing remains difficult.

Although the prisoners have been told they will be executed and that “the soonest ” will be in three days, Indonesian officials stress that the “72-hour rule” is only a minimum and does not prevent the government waiting longer if it chooses.