Indonesia says it has postponed the transfer of eight convicted drug smugglers, including seven foreigners, to a prison island for execution due to technical problems.

The eight are facing execution despite international appeals for clemency. Among them are Andrew Chan and Myuran Sukumaran, the ringleaders of a group of nine Australians arrested in 2005 for attempting to smuggle heroin to Australia from the Indonesian resort island of Bali.

Authorities had said Monday all of the inmates would be transferred this week to Nusa Kambangan prison off the main island of Java.

But Attorney General's Office spokesman Tony Spontana said Tuesday executors surveying the island found it wasn't ready to handle the executions. He said the inmates would be transferred when the location is ready, but didn't give a time frame.