The Indonesian Attorney General's office said on Saturday that the execution time for three Muslim militants responsible for the 2002 Bali nightclub bombings was "very close."
The three men - Imam Samudra, Mukhlas and Amrozi, who was dubbed "the smiling bomber" because of his constant grin during the trial - are on death row for their role in the bomb attacks, which killed 202 people on the resort island of Bali.
"The security is tighter than ever, more police were deployed, (therefore) the time of execution is getting very close," said the attorney general's spokesman, Jasman Pandjaitan.
Pandjaitan said prosecutors had gone to Nusakambangan, a prison island in central Java where the three Bali bombers are being held, to notify them of the timing.
A lawyer for the three men said they had been separated from other inmates, usually an indication that execution will go ahead soon. Local media reported that the execution notifications were submitted to the prison on Friday.
Under Indonesian law, convicts must be given three days' notice of the execution time.
Police presence has increased in Nusakambangan as well as in the home towns of the three men, while security checks of cars and motorbikes across Java has increased.
A makeshift helipad has been prepared near the home of two of the bombers in east Java.
Officials said it would be faster and safer to transport the bodies by helicopter, as under Muslim tradition, burial should take place the same day.
The authorities were concerned that a funeral procession along the roads could lead to chaos and possible violence, particularly if large numbers of militant supporters try to accompany the bodies.
Some analysts have warned there could be a backlash after the execution.