JAKARTA (REUTERS) - The execution of 10 foreigners on death row in Indonesia for drug offences will be carried out together, the attorney general's office said on Thursday.

"Until today there has been no change of plans from the AGO that all execution will be all at once," the attorney general's spokesman Tony Spontana told reporters. "Executions will be done until everything is clear. Whether it will be in March or in April."

The group includes two Australian ctiizens, Andrew Chan and Myuran Sukumaran', whose clemency appeal was postponed until next Thursday because the president's lawyer arrived at Nusakambangan Island prison without signed legal authority, according to Australian media on Twitter.

Sukumaran and Chan, ringleaders of the so-called "Bali Nine" drug trafficking gang, were sentenced to death in 2006 for trying to smuggle heroin out of Indonesia.

They recently lost their appeals for presidential clemency, typically the final chance to avoid the firing squad, and have been moved to Nusakambangan prison island off Java, where their executions are due to take place.

Their lawyers have mounted a final legal challenge to Indonesian President Joko Widodo's decision to reject their pleas for clemency, claiming he failed to assess their rehabilitation or give reasons for his decision.

The appeal was due to be heard today.