PALU, Indonesia — Three Christian militants were executed by firing squad early today for leading attacks on Muslims six years ago that left 70 people dead, a police official and local journalists said.

The men were taken before the firing squad at 12:15 a.m., a senior police officer said, asking not to be identified because he wasn’t authorized to speak to the press. Metro TV and SCTV had similar reports but did not identify their sources.

In carrying out the death sentence, Indonesia ignored an appeal last month by Pope Benedict XVI to spare the men. A Vatican spokesman, the Reverend Federico Lombardi, told the Italian news agency ANSA that news of the execution “was very sad and painful.”

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 in May 2000 — including a machete and gun assault on an Islamic school where dozens of men were seeking shelter.

Security forces braced for sectarian violence, with thousands of police blocking roads leading to the prison where the inmates are being held, standing on street corners and guarding nearby churches.

“I understand they have been killed,” their attorney, Roy Rening, said, adding that he was still awaiting confirmation from the prosecutor’s office.

The case against them has heightened tensions in the world’s most populous Islamic nation and raised questions about the role religion played in punishing those allegedly behind the violence that swept Sulawesi province between 1998 and 2002, killing more than 1,000 people of both religions.

Only a handful of Muslims were convicted in the violence, all for 15 years in prison or less.

The men told relatives and a priest during final prayers at their jail that they were innocent but ready to die.

The planned executions come amid an outcry in many Islamic nations about comments made by Benedict on Islam.

The pontiff last week cited the words of a Byzantine emperor who characterized some of the teachings of the Prophet Muhammad as “evil and inhuman.” He has since said he was “deeply sorry” about the reactions to his remarks and that they did not reflect his own opinions.

The condemned men had said they hoped investigations into the clashes would continue, noting that they had provided authorities with the names of 16 Christians who allegedly instigated some of the worst bloodshed.

The government says its probe is complete.

“My father told me he was not afraid to die, he is not afraid to face his destiny,” Tibo’s son, Robert, said.