Indonesian officials said Wednesday they had deployed thousands of police on Sulawesi island ahead of this week's planned executions of three Christian men found guilty of leading deadly attacks on Muslims six years ago.

Amid complaints that the men did not receive a fair trial, a top Christian leader urged his community not to resort to violence and to pray that the president would grant them a last-minute reprieve.

Government officials, lawyers and priests said the convicts would face a firing squad on Thursday or early Friday.

The case is heightening tensions in the world's most populous Muslim nation and raising questions about the role of religion in deciding punishment for sectarian violence that swept Sulawesi province from 1998 to 2002, killing more than 1,000 people from both communities.

CountryWatch: Indonesia

Thousands of Muslims have taken to the streets in recent weeks demanding the three men be put to death, while Christians have rallied for their lives to be spared.

Fabianus Tibo, 60, Marinus Riwu, 48, and Dominggus da Silva, 42, were found guilty of leading a Christian militia that launched a series of attacks on Muslims in May 2000 — including an assault on an Islamic school that killed at least 70 people.

The attorney general's office said this week the three men could be put to death Thursday, but a priest said after a jailhouse meeting with Tibo that the killings would likely occur the following day.

"The execution is going to take place early Friday," priest Jimmy Tumbelaka said.

Christian groups note that only a handful of people were punished for the violence that wracked Sulewesi, most receiving prison terms of less than 15 years. The bloodshed largely ended with the signing of a peace deal four years ago.

Tibo, Riwu and da Silva were the only people sentenced to death, and human rights activists say it appears unlikely they were the masterminds. Their trial, Christian groups allege, was a sham.

"Everyone is angry, including me," said Rinaldy Damanik, the head of the Central Sulawesi assembly of churches. Regardless, he is calling on his followers to refrain from doing anything that would spark renewed fighting.

There have been isolated acts of religious violence in recent years, most carried out by Islamic militants, from bombings to the beheadings of three school girls.

"My worry is there will be another bombing or shootings" timed to the executions, Damanik said. "If that happens, then I fear the masses will be uncontrollable."

The police chief in Poso, the scene of the worst fighting in early 2000, said the city was calm.

"But we are prepared to handle any reaction against the executions by deploying about 2,000 police, including a mobile brigade, a bomb squad and an anti-terror unit," said Lt. Col. Rudy Sufahriyadi.

In a statement Wednesday, Italy's Foreign Ministry said its Foreign Minister Massimo D'Alema met with his Indonesian counterpart Hassan Wirajuda on the sidelines of the U.N. General Assembly in New York, and urged him not to execute the three Christians.

"D'Alema made a strong appeal" not to go ahead with their execution "for humanitarian reasons," the statement said.

Capital punishment is illegal throughout the European Union, and Pope Benedict XVI last month made an appeal for clemency.