Judges sentenced Islamic militant Hasanuddin to 20 years in prison for masterminding the grisly beheadings of the three teenage Christian schoolgirls three years ago, buying the machetes used to kill them, and leaving a handwritten note at the scene promising more killings to come.

During his trial, Hasanuddin admitted to planning the beheadings as revenge for the deaths of Muslims during sectarian violence that plagued the Poso region from 1999 to 2000.

More than 1,000 Christians and Muslims were killed during the fighting that ended with a peace accord in 2001. Since then sporadic violence has occurred.

Co-conspirators in the beheadings, Lilik Puromo and Irwanto Irano, were sentenced to 14 years in jail in a separate trial.

Last October, three Christian militants were executed for leading an attack on an Islamic boarding school in the Poso region during the sectarian violence in 2000. Many of their supporters claimed the men were innocent and their execution further raised tensions in the region.

Ken Conboy, a terrorism expert and author of several books on terrorism in Indonesia, says the jail terms for the three Muslim militants were unlikely to appease Christians in Poso who were hoping for the death penalty.

"I think they were looking for three for three," said Conboy. "They wanted three executions on the other side to balance the books."

He notes that it is unlikely Hasanuddin will serve his full sentence.

"You also have to realize when they say 20 years over here, 20 years doesn't necessarily mean 20 years. There's appeals and so forth and sentences are cut," added Conboy. "I think it's going to be a hard-core segment that's not going to be very satisfied with that, especially given the crime that was committed. Even by Poso standards that was pretty grisly."

According to intelligence gathered by the Indonesian government, the International Crisis Group, and other terrorism experts, Hasanuddin was the head of the regional terrorist group Jemaah Islamiyah (JI) for the Poso district.

JI, which has been blamed for a series of bombings in Indonesia during the past few years, has split into several factions, one of which operates out of Poso.

On Wednesday Indonesian police said they shot to death a JI militant and arrested several others in a raid on Java island.