Relatives of two men executed in Indonesia arrived back in Australia Saturday on a flight believed to have been carrying the bodies of the pair, whose deaths Prime Minister Tony Abbott has criticised as "cruel and unnecessary".

Andrew Chan, 31, and Myuran Sukumaran, 34, were killed by firing squad on Wednesday over their role in a plot to bring heroin to Australia from the Indonesian resort island of Bali, despite international pleas for clemency.

The Australian Broadcasting Corporation said the bodies were on the flight which touched down in Sydney early Saturday and also carried Sukumaran's parents, brother and sister and Chan's wife Febyanti Herewila.

The Department of Foreign Affairs and Trade was unable to confirm that the men's bodies were on the plane.

Chan's mother and brother arrived back in Sydney on Friday after the repatriation of the bodies was delayed.

Chan and Sukumaran were among seven foreigners executed in Indonesia in the early hours of Wednesday.

They had spent a decade in prison for their role in masterminding the so-called 'Bali Nine' group of smugglers, during which time Chan had become a Christian pastor and Sukumaran had studied art.

Prime Minister Abbott criticised the executions of the men, which has cast a shadow over Australia's relationship with its important neighbour Indonesia, as "cruel" and "unnecessary".

But he described as "odd" a decision by the Australian Catholic University (ACU) to introduce scholarships in memory of the executed pair for Indonesian students wishing to study in Australia.

"We did this because ACU is committed to the dignity of the human person, and that applies equally to all human beings: victims as well as to those who have been convicted of crimes," Vice Chancellor Greg Craven said.

Abbott said the men had met their deaths with a "kind of nobility", but he questioned whether that justified establishing scholarships in their name.

"I know part of Christian faith is forgiveness, but another part of Christian faith is calling people to be their best selves," he told commercial radio late Friday.