A presidential pardon is the only legal option left for three Islamic militants on death row for the 2002 Bali bombings after the top court rejected their final appeal, a district court official said on Friday.

The Supreme Court's rejection of their third appeal for a case review takes the bombers, who have repeatedly said they will not seek presidential clemency, a step closer to execution by firing squad although there is no specific date.

The three Islamic militants - Amrozi, his brother Mukhlas alias Ali Ghufron and Imam Samudra - have been on death row since 2003 when a Bali court sentenced them to death for their roles in the nightclub bombings that killed 202 people.

"Based on the letter from the Supreme Court, a case review appeal can only be done once," Nyoman Gede Wirya, head of Denpasar district court, told reporters on Friday.

"By this letter, the case review process is then finished, and the next legal avenue attempt there is is a right to ask for pardon."

Bali's Denpasar District Court will send the Supreme Court letter to the families and the convicts to ask if they will exercise the right to request a pardon.

The bombers' lawyer said the letter would reach them by next week, when the bombers would be asked to decide if they want to seek clemency.

"We will ask them later whether they will use their right to ask for a pardon or not," Mahendradatta, the lawyer, said.

The Supreme Court turned down their third appeal for a case review, saying convicts can only appeal for a case review once.

In most cases, only one case review is allowed, although there are a handful of examples when the Supreme Court has considered a second review.

The three have repeatedly told the media they are ready to die as martyrs and will not seek presidential clemency.

They are being held in a maximum-security jail on Nusakambangan island off Central Java, hundreds of kilometres from their families who live in East and West Java.

Indonesia does not make public the timing and exact location of executions, but a deputy attorney-general in May said it would be done in Central Java.