Two Australian drug convicts were notified on Saturday that they will be executed by firing squad in 72 hours at the Indonesian prison island of Nusakambangan, a source with direct knowledge of the matter said.

"A 72 hours notice of execution was given to Bali 9 death row inmates Andrew Chan and Myuran Sukumaran on Saturday," the source told Reuters, declining to comment further.

A total of seven convicts have received notifications of their imminent execution, said a lawyer for a Nigerian death row inmate who is among the group.