JAKARTA (Reuters) -- Three Indonesian Christian militants convicted of leading a mob that killed Muslims will be executed on Thursday, the convicts' lawyer said, but there was no immediate word on the fate of their clemency appeals.

Fabianus Tibo, Marianus Riwu and Dominggus Silva were sentenced to death in 2001 after being found guilty of leading a Christian mob in an attack that killed more than 200 people at an Islamic boarding school during Muslim-Christian clashes in Central Sulawesi's Poso region.

They have appealed to the Indonesian president for clemency and Pope Benedict has also called on Indonesia to stop the execution.

"Yesterday the prosecutors gave the letter of notice (to the convicts) for the execution to take place on Sept. 21," Roy Rening, the lawyer for the convicts, told Reuters.

The trio were scheduled to face a firing squad at a secret location in Palu, the capital of Central Sulawesi province last month, but the decision was delayed after demonstrations by thousands of Indonesians, and the Pope's appeal.

Muslim-Christian clashes erupted in Central Sulawesi from late 1998 to 2001, killing 2,000 before a peace accord took effect.

Three Islamic militants have also been sentenced to death for their leading roles in the 2002 Bali nightclub bombings that killed 202 people.

The attorney-general's office said on Aug. 21 their executions would be delayed for a judicial review planned by defense lawyers.

Around 85 percent of Indonesia's 220 million people follow Islam, but some areas in eastern Indonesia have roughly equal proportions of Muslims and Christians.